concurring in part and concurring in the judgment:
I concur in the judgment and in Sections I, II-A, II-C, and III of Judge Alarcon’s opinion. I agree that 20 U.S.C § 1414(d)(l)(B)(ii) requires that at least one regular education teacher be included on an Individualized Education Program (“IEP”) team, and that the omission of a regular education teacher from M.L.’s IEP team was procedural error. However, I do not agree with the per se “structural defect” analysis adopted by Judge Alarcon in Section II-B. I write separately to make clear that our court’s procedural analysis under IDEA does not start and end with automatic reversal based on a theory of structural error. Instead, we must assess the school district’s error for harmlessness — in accord with our precedent in Target Range, Amanda J., and Shapiro — by considering whether the procedural error resulted in a loss of educational opportunity or significantly restricted parental par*652ticipation in the IEP formation. IDEA procedural error may be held harmless in appropriate cases, and this may include cases involving a mistake in how the IEP team was constituted. Although Judge Clifton in dissent and I in concurrence agree on the rejection of structural error and on the standard for assessing harmless error, we reach different conclusions in the application of the governing standard.1 We both agree that the harmless error assessment turns here on whether there was a “loss of educational opportunity” for M.L. Applying this correct test for harmless error, I further conclude that the error in composition of the IEP team, under the circumstances of this case, caused a violation of the IDEA and requires reversal of the district court’s order granting summary judgment.
In Section I, I explain what I believe to be the controlling test for harmless error under our case law and why I believe a structural defect analysis is inapplicable in an IDEA context. In Section II, I apply the harmless error test to the facts in the record, and conclude that the procedural error in this case was not harmless. Henee, I concur in the judgment reached by Judge Alarcon, but not the structural error analysis that he advances.
I
A
In Board of Education v. Rowley, 458 U.S. 176, 206-207, 102 S.Ct. 3034, 73 L.Ed.2d 690 (1982), the Supreme Court established a framework for IDEA review: “First, has the State complied with the procedures set forth in the Act? And second, is the individualized educational program developed through the Act’s procedures reasonably calculated to enable the child to receive educational benefits?” In applying this standard, our cases (and those of our sister circuits) have not adopted a structural error approach. Instead, each case treats the procedural prong of Rowley as having two subparts: First, was there a procedural violation of the IDEA, and second, if there was error, did it affect the substantive rights of the plaintiff. See 28 U.S.C. § 2111 (“On the hearing of any appeal or writ of certiorari in any case, the court shall give judgment after an examination of the record without regard to errors or defects which do not affect the substantial rights of the parties.”).
The test for determining whether IDEA procedural error affects the substantial rights of the parties has been established by our prior precedent. In W.G. v. Board of Trustees of Target Range Sch. Dist. No. 23, 960 F.2d 1479, 1484 (9th Cir.1992) ("Target Range"), we stated: "Procedural flaws do not automatically require a finding of a denial of a FAPE. However, procedural inadequacies that result in the loss of educational opportunity, or seriously in*653fringe the parents' opportunity to participate in the IEP formulation process, clearly result in the denial of a FAPE." Id. (internal citations omitted).2 Our more recent cases follow the Target Range procedural error analysis. See Shapiro v. Paradise Valley Unified Sch. Dist., 317 F.3d 1072, 1079-1080 (9th Cir.2003) (quoting and applying the Target Range standard in holding that the omission of a child's parents and a teacher from her prior school were procedural violations in the creation and composition of her IEP team which amounted to the denial of a FAPE because they "resulted in the loss of educational opportunity for [the child]") superseded on other grounds by 20 U.S.C. § 1414(d)(1)(B); Amanda J. v. Clark County Sch. Dist., 267 F.3d 877, 891-892 (9th Cir.2001) (applying the Target Range analysis to an "egregious" IDEA procedural error instead of granting automatic reversal). In sum, our precedents in Target Range, Amanda J., and Shapiro establish that not all procedural violations by a school district in implementing the IDEA will necessarily result in the denial of a FAPE. Procedural error — including in M.L.'s case the omission of members of an IEP team — constitutes the denial of a FAPE only when it results in lost educational opportunity for the child, or when it significantly restricts parental participation in the IEP formation. See Target Range, 960 F.2d at 1484; Shapiro, 317 F.3d at 1079; Amanda J., 267 F.3d at 892; Ms. S. ex rel. G. v. Vashon Island Sch. Dist., 337 F.3d 1115, 1129 (9th Cir.2003) superseded on other grounds by 20 U.S.C. § 1414(d)(1)(B).
B
Judge Alarcon characterizes the absence of a regular education teacher from M.L.'s IEP team as a "structural error" or a "structural defect" that is not subject to harmless error analysis. Judge Alarcon's Opinion at 612. In doing so, he extrapolates from the criminal context, where the Supreme Court has immunized certain errors that affect the constitutional rights of defendants from harmless error review. See generally Arizona v. Fulminante, 499 U.S. 279, 309-310, 111 S.Ct. 1246, 113 L.Ed.2d 302, (1991); Chapman v. California, 386 U.S. 18, 22-24, 87 S.Ct. 824, 17 L.Ed.2d 705 (1967).3
While one might in other contexts applaud a creative solution to a difficult case, I find this structural error analysis strik*654ingly inapplicable in our civil case context, where we are asked to assess whether a school district has infringed a child’s rights to education consistent with the IDEA. Even in the realm of constitutional error in criminal prosecutions, where life and liberty are at stake, the Court has made clear that the situations where we will find structural error requiring automatic reversal are a “very limited class of cases.” Johnson v. United States, 520 U.S. 461, 468, 117 S.Ct. 1544, 137 L.Ed.2d 718 (1997).4 Structural errors are the “exception and not the rule,” Rose v. Clark, 478 U.S. 570, 578, 106 S.Ct. 3101, 92 L.Ed.2d 460 (1986), and “most constitutional errors can be harmless.” Fulminante, 499 U.S. at 306, 111 S.Ct. 1246.
Judge Alarcon cites no precedent applying structural error in civil cases in our circuit, and I have found none, nor has he cited any IDEA-specifie cases in our circuit applying a structural error test to procedural error.5 Moreover, Judge Alar-con does not cite any examples of IDEA structural error analysis from other circuits. In fact, our sister circuits have consistently rejected per se IDEA structural error arguments, and instead have adopted case-by-case, harmless error inquiries similar to our standard, which I have reviewed above.6 Nor does the strue-*655tural error position in IDEA litigation find any support in the text or legislative history of the IDEA. In the absence of guidance from the Court or Congress, we should conclude that IDEA cases are subject to the general principle of harmless error that applies generally in civil and criminal law contexts. See 28 U.S.C. § 2111; Fed R.Crim. P. 52(a); Fed. R.Civ.P. 61.
Judge Alarcon’s structural error analysis disclaims a general applicability and purports to be limited, advocating a per se rule of reversal only for the violation of one procedural requirement of the IDEA: 20 U.S.C. § 1414(d)(l)(B)(ii), the requirement that an IEP team include a regular classroom teacher. However, Judge Alar-con sets forth no persuasive qualitative distinction between § 1414(d)(l)(B)(ii) and the other procedural requirements of the IDEA, which too are important.7 Consequently, Judge Alarcon’s opinion posits no necessary or logical stopping point prohibiting future courts from applying a structural error approach to virtually any IDEA procedural error. In my view, the best means by which to differentiate between such errors is to evaluate each one individually — as colored by each case’s particular facts — and to apply a uniform standard that assesses lost educational opportunity or lost parental participation, not by adopting a per se rule that insulates a subset of errors from future review. It should not be forgotten that, in interpreting IDEA, we, like the school district, parents, and the advocates participating in administrative hearing and in the courts, are trying to determine what is best for a disabled child.
II
Accordingly, my analysis takes me back to where I commenced, applying the Target Range standard to determine whether the procedural error in IEP team composi*656tion amounted to denial of a FAPE by either excluding appropriate parental participation or causing a lost educational opportunity for the child. This case poses no genuine issue of whether a parent of M.L. was excluded from the IEP process,8 and so the controlling issue becomes whether the failure to include a regular education teacher on the IEP team resulted in a “loss of educational opportunity” within the meaning of the test established in Target Range. I am persuaded that, under the total circumstances, M.L. lost an educational opportunity because the FWSD violated the procedural requirements of the IDEA by failing to include a participating regular education teacher on the IEP team.9
The statutory requirement that an IEP team for a disabled child who is or may be in regular education must include a regular education teacher is not merely technical. A regular education teacher may have insights or perspectives that aid the process of IEP formation. We need not say that error in composition of an IEP team is always prejudicial and invariably results in the denial of a FAPE.' Rather, we should assess the circumstances of each case, and here the record demonstrates that the failure to include Ms. Ramsey or Ms. Wicks or any other regular education teacher on the participating IEP team deprived M.L. of an educational opportunity.
This conclusion is unmistakable for several reasons. First, there is the IDEA’S statutory preference for mainstreaming. The IDEA favors mainstreaming the education of a disabled child to “the maximum extent appropriate” given the nature of the child’s disability. 20 U.S.C. § 1412(a)(5)(A).10 When mainstreaming is pursued with a disabled child, and the child’s education proceeds in the “Least Restrictive Environment,” as set forth in 20 U.S.C. § 1412(a)(5)(A), the crucial purposes and requirements of IDEA are realized: The disabled child receives the benefit of observing and working with those who are not disabled, which can provide the disabled child with both educational and non-academic benefits. Children who are not disabled are given the opportunity to' become better acquainted with their disabled peers, which may help avoid stereotyping, lessen prejudice, and prepare all students to. work together in society. Most importantly, mainstreaming is the mechanism for fulfilling the statutory goal that the disabled child be educated in the least restrictive setting, which experience tells us is best for the child’s development. *657See e.g., Alan Gartner & Dorothy K. Lipsky, Beyond Special Education: Toward a Quality System for All Students, 57 Harv. Educ. Rev. 367, 375 (1987) (concluding that there is a “substantial and growing” body of evidence that supports the academic and emotional developmental value of mainstreaming). The parents of disabled children do not have to prove a regular education environment is best for their children; rather, it is the school district’s burden to explain in the IEP the extent to which a child cannot participate in regular education activities. 20 U.S.C. § 1414(d)(l)(A)(iv).
Second, Ms. Wicks, M.L.’s prior regular education teacher, had written to the FWSD, informing the school district that M.L. had made “good progress” in her class, which was comprised of twelve non-disabled students and four or five with “special needs,” and recommending that M.L. remain in regular education during his kindergarten year. Third, the FWSD had appointed a regular education teacher to the IEP team, but inexplicably went forward with the IEP planning meeting without that teacher’s presence and participation. Fourth, M.L.’s past IEP and placement demonstrated that it was at least possible to conclude that M.L. could be placed in a regular education classroom.
I certainly recognize that M.L.’s education in a regular classroom poses serious challenges for him, for classmates, for instructors, and for administration. That is clear from the record before us. But under the totality of circumstances, we cannot readily conclude that the statutory violation in not having a regular education teacher participate on the IEP team was harmless. To the contrary, there is a strong likelihood that mainstreaming opportunities for M.L. would have been better considered had a regular education teacher taken part in the program’s preparation, and that more mainstreaming might have been permitted for M.L. under the IEP. Hence, I do not believe that we can properly hold that the error in IEP team composition here was harmless.
Because I conclude on this record that we must hold that the FWSD’s IEP process caused a “loss of educational opportunity,” and the district court’s conclusion was error,11 I need not reach the second step in the Rowley analysis, i.e., whether the IEP was “reasonably calculated to enable the child to receive educational benefits.” Rowley, 458 U.S. at 207, 102 S.Ct. 3034; see also 28 U.S.C. § 2111 (providing that”[o]n the hearing of any appeal ... in any case, the court shall give judgment after an examination of the record without regard to errors or defects which do not affect the substantial rights of the parties”).12
. Judge Clifton's dissent states:
Finally, I agree with Judge Gould, as expressed in Section I of his opinion, that a structural error analysis is not supported by our caselaw and has no place in the IDEA context. As Judge Gould correctly observes, a procedural violation constitutes a denial of a free and appropriate public education only when it results in a lost educational opportunity for the child or significantly restricts parental participation in formation of the IEP.
Dissent at 658.
Judge Clifton in his dissent concludes that the error in composition of the IEP team was harmless under the same standard I apply. Our differences turn in part on our disagreement on whether the assessment of loss of educational opportunity is a question of fact to be reviewed for clear error, or a mixed question of fact and law, to be reviewed de novo, as can be seen from a comparative review of our opinions, which apply the same standard but reach contrary results.
. In Target Range, we addressed whether omissions in the formulation of an IEP constituted the denial of a free appropriate public education ("FAPE”). The district court had held in favor of the plaintiff family, finding that the Target Range school district had failed to include important parties — the child's parents, regular education teacher, or a representative of the private school the child had also attended — in the IEP development. 960 F.2d at 1483-1484. We affirmed, holding that “Target Range clearly did not comply with the procedures required by the IDEA.” Id. Our analysis elaborated that procedural errors do not amount to a per se denial of a FAPE, but, rather, that we will find that a FAPE has been denied where procedural inadequacies result in the "loss of educational opportunity,” or when such errors "seriously infringe” parental ability to participate in the IEP process. Id. at 1484.
. In support of his extension of this concept to our civil case, Judge Alarcon cites two 1979 cases external to our circuit addressing promotional evaluation boards in the United States Army, Doyle v. United States, 220 Ct.Cl. 285, 599 F.2d 984 (Cl.Ct.1979), and Dilley v. Alexander, 603 F.2d 914 (D.C.Cir.1979). Doyle and Dilley analogized to the structural defect cases discussed in Chapman, holding that the omission of statutorily-mandated reserve officers from military boards evaluating reservists for promotion was a structural error which was per se prejudicial and precluded any subsequent harmless error review. Doyle, 599 F.2d at 995; Dilley, 603 F.2d at 921-924.
. In emphasizing the narrowness of this limited universe of structural defects warranting per se relief, the Supreme Court, in Neder v. United States, 527 U.S. 1, 8, 119 S.Ct. 1827, 144 L.Ed.2d 35 (1999), cited key cases identifying such defects:
Johnson v. United States, 520 U.S. 461, 468, 117 S.Ct. 1544, 137 L.Ed.2d 718 (1997) (citing Gideon v. Wainwright, 372 U.S. 335, 83 S.Ct. 792, 9 L.Ed.2d 799 (1963) (complete denial of counsel)); Tumey v. Ohio, 273 U.S. 510, 47 S.Ct. 437, 71 L.Ed. 749 (1927) (biased trial judge); Vasquez v. Hillery, 474 U.S. 254, 106 S.Ct. 617, 88 L.Ed.2d 598 (1986) (racial discrimination in selection of grand jury); McKaskle v. Wiggins, 465 U.S. 168, 104 S.Ct. 944, 79 L.Ed.2d 122 (1984) (denial of self-representation at trial); Waller v. Georgia, 467 U.S. 39, 104 S.Ct. 2210, 81 L.Ed.2d 31 (1984) (denial of public trial); Sullivan v. Louisiana, 508 U.S. 275, 113 S.Ct. 2078, 124 L.Ed.2d 182 (1993) (defective reasonable doubt instruction).
. The two Ninth Circuit cases cited by Judge Alarcon to define structural error both concern the constitutional rights of criminal defendants. United States v. Recio, 371 F.3d 1093, 1101 (9th Cir.2004); Rice v. Wood, 77 F.3d 1138, 1141 (9th Cir.1996). They are inapposite in this IDEA context.
. Adam J. v. Keller Indep. Sch. Dist., 328 F.3d 804, 812 (5th Cir.2003) (citing Target Range, 960 F.2d at 1484, and holding that "even if the determination of [the child's] IEP was procedurally deficient in some respects, he has not established that any procedural deficiency resulted in a loss of educational opportunity or infringed his parents' opportunity to participate in the IEP process"); DiBuo v. Bd. of Educ., 309 F.3d 184, 191 (4th Cir.2002) (rejecting the argument that a procedural IDEA violation should constitute a per se denial of a FAPE); MM v. Sch. Dist. of Greenville County, 303 F.3d 523, 533 (4th Cir.2002) (holding that "[w]hen such a procedural defect exists, we are obliged to assess whether it resulted in the loss of educational opportunity for the disabled child, or whether, on the other hand, it was a mere technical contravention of IDEA"); T.S. v. Indep. Sch. Dist. No. 54, 265 F.3d 1090, 1095 (10th Cir.2001) ("Procedural defects alone do not constitute a violation of the right to a FAPE unless they result in the loss of educational opportunity."); Knable v. Bexley City Sch. Dist., 238 F.3d 755, 765 (6th Cir.2001) ("[A] procedural violation of the IDEA is not a per se denial of a FAPE; rather, a school district's failure to comply with the procedural requirements of the Act will constitute a denial of a FAPE only if such violation causes substantive harm to the child or his parents.... [P]rocedural violations that deprive an eligible student of an [IEP] or result in the loss of educational opportunity also will constitute a denial of a FAPE under the IDEA."); Weiss v. Sch. Bd. of Hillsborough County, 141 F.3d 990, 996 (11th Cir.1998) ("For the [plaintiff family] to prove that [their child] was denied a FAPE, they must show harm to [the child] as a result of the alleged procedural violations. Violation of any of the procedures of the IDEA is not a *655per se violation of the Act."); Heather S. v. Wisconsin, 125 F.3d 1045, 1059 (7th Cir.1997) (quoting the Target Range standard); Indep. Sch. Dist. No. 283 v. S.D., 88 F.3d 556, 562 (8th Cir.1996) ("An IEP should be set aside only if procedural inadequacies compromised the pupil's right to an appropriate education, seriously hampered the parents' opportunity to participate in the formulation process, or caused a deprivation of educational benefits.") (internal quotation marks omitted); Murphy v. Timberlane Reg. Sch. Dist., 22 F.3d 1186, 1196 (1st Cir.1994) ("[N]ot every procedural irregularity gives rise to liability under the IDEA. Nevertheless, procedural inadequacies [that have] compromised the pupil's right to an appropriate education ... or caused a deprivation of educational benefits are the stuff of successful IDEA actions.") (internal quotation marks omitted); Hampton Sch. Dist. v. Dobrowolski, 976 F.2d 48, 52-53 (1st Cir.1992).
. Judge Alarcon emphasizes that the 1997 IDEA amendments revised the language of this provision, changing the IEP team requirement from the current teacher, when general education is a real possibility, to both a regular classroom teacher and a special education teacher. Op. at 643; compare 20 U.S.C. § 1414(d)(1)(B) (2003), with 20 U.S.C. § 1401(a)(20) (1996). But the 1997 IDEA amendments were numerous and substantive, affecting the entire statutory scheme, and reworking several procedural requirements, including other aspects of the IEP process. See generally Dixie Snow Huefner, The Individuals With Disabilities Education Act Amendments of 1997, 122 Ed. L. Rep. 1103 (1998). Other "[m]ajor new requirements were added to the IEP section." Id. at 1112-15. We accounted for Congress’s purpose and focus, when it amended the provision, by our holding that it had been violated, and by rejecting the school district’s array of defensive arguments. Yet, there is nothing in the statute or its regulations from which to conclude that those changes necessitate that § 1414(d)(l)(B)(ii) have its own structural defect procedural error analysis, separate and apart from the analysis applied to the other equally important IDEA procedural requirements, and at odds with the general course of civil and even criminal law.
. Appellants do not contend that the FWSD’s procedural error significantly restricted their participation in the IEP process.
. We review de novo the district court's conclusions of law. Gregory K. v. Longview Sch. Dist., 811 F.2d 1307, 1310 (9th Cir.1987). Judge Clifton concludes that the question of harmless error is one of fact and that we review the district court’s findings for clear error. Dissent at 662-63. His analysis must concede, however, that the district court did not "fram[e][its] discussion in terms of 'loss of educational opportunity' ” and that "the meaning of the phrase 'lost educational opportunity' ” is a legál question. Dissent at 659, 662 n. '4. For these reasons, the question of whether M.L. has "los[t] an educational opportunity” under the IDEA is a mixed question of law and fact which we review de novo. Gregory K., 811 F.2d at 1310; Target Range, 960 F.2d at 1483 (holding that the issue of whether a proposed IEP constitutes a FAPE is a mixed question of law and fact that we review de novo).
.To better accomplish this goal and accommodate those disabled children who might require specialized tools and supplements, Congress mandated that a child could only be removed from the regular class environment when the "use of supplementary aids and services could not be achieved satisfactorily” in the regular educational environment. 20 U.S.C. § 1412(a)(5)(A).
. I reach this conclusion initially on my premise that the issue is a mixed question of fact and law, not predominantly factual in light of the IDEA’S statutory preference for mainstreaming; but even if I were to view this issue under the "clear error” standard, I would still conclude that the district court’s grant of summary judgment on the theory that there was no lost educational opportunity was reversible error.
. The dissent concludes that we must affirm because the district court found "that the program developed by the IEP team was the best placement for M.L., because it maximized the academic and nonacademic benefits available to him.” Dissent at page 659. But, the district court made its findings regarding whether the IEP was reasonably calculated to enable the child to receive educational benefits without the benefit of the views and expertise of a regular classroom teacher having been expressed at the critical IEP team meeting to discuss M.L. The IDEA mandates that a regular classroom teacher be a member of the IEP team. Although I do not think a per se reversal follows from a violation under our precedent, there is no doubt that the inclusion of a regular education teacher on the IEP team promotes the purposes of the IDEA. We *658ought not to speculate here that noncompliance with the procedural standards mandated in the IDEA did not matter. Because the failure of the school district to include a regular classroom teacher on the IEP team, conjoined with the other circumstances reviewed above that made regular education for M.L. a distinct possibility, we cannot say the error was harmless. For these reasons, and because of my disagreement on the standard of review, see supra notes 9 and 11, I cannot agree with my dissenting colleague’s conclusion that if a regular classroom teacher had participated on the IEP team “there was [not] a realistic possibility that it would have resulted in a different assignment for M.L.’’ Dissent at page 664.