OPINION BY
Judge SMITH-RIBNER.The Indiana Area Education Association (Association) appeals from the order of the Court of Common Pleas of Indiana County that vacated an arbitrator’s award sustaining the Association’s grievance filed against the Indiana Area School District (School District). The grievance arose out of the School District’s denial of the rights and status under the collective bargaining agreement (CBA) to the school nurse assistant RNs (nurse assistant RNs). The questions for review are whether the arbitrator had authority to decide the applicability of the CBA to the nurse assistant RNs added to the bargaining unit after the execution of the CBA pursuant to an order of the Pennsylvania Labor Relations Board (Board) and whether the trial court failed to follow its limited scope of review.
I
On April 30, 2001, the School District and the Association entered into a CBA covering the period July 1, 2001 through June 30, 2007. The CBA recognized the Association “as the exclusive representative for purposes of collective bargaining with respect to wages, hours and other terms and conditions of employment.” Article II, Section 1 of the CBA; Reproduced *368Record (R.R.) at 209a. The CBA provided:
The unit deemed appropriate in the aforementioned certification shall include all eligible employees under the [Public Employe Relations] Act in the following categories under the jurisdiction of the District:
• Classroom Teachers Under Contract
• Nurses Under Contract
• Dental Hygienists Under Contract
• Guidance Counselors Under Contract
• Speech Therapists Under Contract
• Librarians Under Contract
.... The term ‘employee’ and ‘teacher’ are used interchangeably herein.
Article II, Section 2; R.R. at 210a (emphasis added).
On March 20, 2002, the Association filed a petition with the Board for unit clarification to include the nurse assistant RN positions in the bargaining unit. After the School District agreed to their inclusion, the Board issued a Nisi Order of Unit Clarification on September 9, 2002 amending the December 10, 1970 certification to include the nurse assistant RN positions in the unit. At relevant times, the School District employed three certified school nurses at three junior and senior high schools and three nurse assistant RNs at three elementary schools.
By letter dated September 19, 2002, the Association requested confirmation from the School District that the nursing assistant RNs were being provided the same rights, benefits and privileges as other nurses in the bargaining unit. The School District responded that because the nurse assistant RNs were not identified in the CBA, their salary schedule, fringe benefits and leave entitlement should be negotiated. On October 28, 2002, the Association filed a grievance on behalf of the nurse assistant RNs alleging that the School District violated the CBA by denying bargaining unit rights and status. The School District refused to schedule a hearing to process the grievance or to select an arbitrator from the list provided by the Bureau of Mediation, stating that the issue was not arbitrable but that it would negotiate as to the new category of nurse assistant RN.1
On February 6, 2003, the School District filed an unfair labor practice charge against the Association under Section 1201(b)(3) of the Public Employe Relations Act (PERA), Act of July 23,1970, P.L. 563, as amended, 43 P.S. § 1101.1201(b)(3) (refusing to bargain collectively in good faith with a public employer), docketed at No. PERA-C-03-41-W (Case No. 41). On February 20, 2003, the Association filed an unfair labor practice charge against the School District under Section 1201(a)(1) and (5) (interfering, restraining or coercing employees in the exercise of the rights under the Act and refusing to bargain collectively in good faith with an employee representative), docketed at No. PERA-C-03-61-W (Case No. 61). The matters were consolidated for hearing.
In the Proposed Decision and Order issued March 1, 2004 in Case No. 41, the hearing examiner rejected the Association’s argument that its refusal to bargain over the nurse assistant RN position did not constitute an unfair labor practice because it had a “sound arguable basis” for the refusal. See State System of Higher Education v. APSCUF, 20 PPER ¶ 20125 *369(Final Order, 1989) (holding that a union does not commit an unfair labor practice by refusing to bargain if the union has a sound arguable basis for believing that its action is in conformity with a collective bargaining agreement). Concluding that the Association failed to present evidence to establish that the duties of the certified school nurse and the nurse assistant RN positions were substantially similar, the hearing examiner ordered the Association to submit to the School District a written offer to bargain over the wages, hours and terms and conditions of the nurse assistant RN position. The Board dismissed the Association’s exceptions and made the hearing examiner’s Proposed Decision and Order absolute and final. The Association did not appeal.
In a separate Proposed Decision and Order issued in Case No. 61 the same day, the hearing examiner found that the School District committed unfair labor practices by refusing to arbitrate the Association’s grievance. The hearing examiner ordered the School District to submit an offer to the Association to arbitrate the grievance. The Board dismissed the School District’s exceptions, rejecting the argument that there could not be both a duty to bargain and a duty to arbitrate the grievance. The School District did not appeal from this final order.
Thereafter, the School District and the Association selected an arbitrator by mutual consent. After a hearing on October 5, 2004, the arbitrator concluded that the interpretation and application of the CBA was central to the outcome of the case and that arbitration was the proper forum for resolving the dispute. He found that the School District had assigned three certified nurses to support the newly hired nurse assistant RNs since the 1999-2000 school year, that the major difference between the certified nurses and the nurse assistant RNs was that the former held bachelor degrees and teaching certificates issued by the Pennsylvania Department of Education and that the nurse assistant RNs’ work was substantially the same as that of the certified nurses. The arbitrator concluded that, as members of the bargaining unit and as professional employees, the nurse assistant RNs were entitled to all rights and benefits provided to other professional employees, and he sustained the grievance and extended salary and fringe benefits under the CBA to the nurse assistant RNs based on their credited service and educational credits. The arbitrator denied interest on the award, and he retained jurisdiction to allow the parties to work out the remedy amount.
On appeal, the trial court vacated the arbitration award and overruled the grievance because, in its view, the arbitrator’s jurisdiction rested upon a finding of substantial similarity of the nurse assistant RN and school nurse positions; the identical factual issue of substantial similarity of the two positions could be inferred from the Board’s decision in Case No. 41 where the Association had a full and fair opportunity to litigate the issue; the parties were bound by that finding under the doctrine of collateral estoppel; and the finding of substantial similarity was inconsistent with the Board’s decision in Case No. 41. The trial court held that the arbitrator’s finding of his jurisdiction was erroneous as a matter of law.2
*370II
The Association argues that the trial court erred because the arbitrator had the authority to decide the issue of the applicability of the CBA to the employees who were newly added to the bargaining unit and because the trial court failed to follow the very limited scope of reviewing the arbitrator’s award. Section 903 of the PERA, 43 P.S. § 1101.903, provides that “[a]rbitration of disputes or grievances arising out of the interpretation of the provisions of a collective bargaining agreement is mandatory” and that the final step of the arbitration process must “provide for a binding decision by an arbitrator.... ”
In State System of Higher Education, (Cheyney University) v. State Coll. Univ. Prof'l Ass’n (PSEANEA), 560 Pa. 135, 149-150, 743 A.2d 405, 413 (1999), the Pennsylvania Supreme Court set forth the essence test standard for trial courts to follow in reviewing challenges to an arbitrator’s award under the PERA:
[T]here is a strong presumption that the Legislature and the parties intended for an arbitrator to be the judge of disputes under a collective bargaining agreement. That being the case, courts must accord great deference to the award of the arbitrator chosen by the parties.... The arbitrator’s award must draw its essence from the collective bargaining agreement. ... First, the court shall determine if the issue as properly defined is within the terms of the collective bargaining agreement. Second, if the issue is embraced by the agreement, and thus, appropriately before the arbitrator, the arbitrator’s award will be upheld if the arbitrator’s interpretation can rationally be derived from the collective bargaining agreement. That is to say, a court will only vacate an arbitrator’s award where the award indisputably and genuinely is without foundation in, or fails to logically flow from, the collective bargaining agreement.
See Office of Attorney General v. Council 13, American Fed’n of State, County & Mun. Employees, 577 Pa. 257, 844 A.2d 1217 (2004) (holding that strict adherence to the essence test is mandated by strong historical preference for swift and efficient means of settling disputes under a collective bargaining agreement by grievance procedures culminating in binding arbitration). See also Somerset Area School District v. Somerset Area Educ. Ass’n, 899 A.2d 1170 (Pa.Cmwlth.), appeal denied, 589 Pa. 735, 909 A.2d 307 (2006) (reiterating limited nature of essence test review). Moreover, limited judicial review under the essence test applies not only to an arbitration award but to the determination by an arbitrator of his or her jurisdiction as well. Juniata-Mifflin Counties Area Vocational-Technical School v. Corbin, 547 Pa. 495, 691 A.2d 924 (1997).
In State System of Higher Education v. Ass’n of Pennsylvania State Coll. & Univ. Faculties (SSHE I), 800 A.2d 983 (Pa.Cmwlth.2002), the Court considered the issue of whether the existing collective bargaining agreement applied to the non-faculty athletic trainers who were newly added to the bargaining unit. The Court adopted the holding in Howell Educ. Secretaries Ass’n v. Howell Public Schools, 130 Mich.App. 546, 343 N.W.2d 616 (1983), and held in SSHE I that if the non-faculty trainers’ duties were “substantially similar” to the duties of faculty trainers covered by the collective bargaining agreement, then the terms of the agreement would apply to non-faculty trainers and if not a new contract must be negotiated. *371Subsequently, in State System of Higher Education v. Pennsylvania Labor Relations Board, 821 A.2d 156 (Pa.Cmwlth.2003), the Court reaffirmed the SSHE I holding and rejected the argument that employment terms for positions newly accreted into a bargaining unit must be negotiated in all circumstances.
The trial court misapplied the doctrine of collateral estoppel when it concluded that the arbitrator lacked jurisdiction over the Association’s grievance due to the Board’s previous determination regarding the substantial similarity of the two positions in Case No. 41. Collateral estoppel precludes the re-litigation of an issue determined in a previous action under the following circumstances:
(1) the issue decided in the prior case is identical to the one presented in the later action; (2) there was a final adjudication on the merits; (3) the party against whom the plea is asserted was a party or in privity with a party in the prior case; (4) the party or person privy to the party against whom the doctrine is asserted had a full and fair opportunity to litigate the issue in the prior proceeding; and (5) the determination in the prior proceeding was essential to the judgment.
Office of Disciplinary Counsel v. Kiesewetter, 585 Pa. 477, 484, 889 A.2d 47, 50-51 (2005).
Under Section 1301 of the PERA, 43 P.S. § 1101.1301, the Board has exclusive jurisdiction to hear unfair labor practice charges. Case No. 41 concerned whether the Association committed an unfair labor practice by refusing to bargain over the employment terms and conditions of the nursing assistant RNs. The resolution of that issue in turn was dependent upon a determination of whether the Association had a sound arguable basis for refusing to bargain. Case No. 61 concerned the School District’s refusal to participate in arbitration after its denial of CBA rights and benefits to the employees. Clearly, the issues were separate.
It is well settled that the arbitrator has the sole jurisdiction to decide the arbitrability of an issue in the first instance. See Pennsylvania Labor Relations Board v. Bald Eagle Area School District, 499 Pa. 62, 451 A.2d 671 (1982); Chester Upland School District v. McLaughlin, 655 A.2d 621 (Pa.Cmwlth.1996), aff'd, 544 Pa. 199, 675 A.2d 1211 (1996). See also Philadelphia Housing Authority v. Pennsylvania Labor Relations Board, 75 Pa.Cmwlth. 199, 461 A.2d 649 (1983) (refusing to hold the Board powerless to investigate unfair labor practice charge because of availability of grievance arbitration under collective bargaining agreement). The mere existence of “a factual determination relevant to both the arbitration and the unfair practice proceedings, does not render the unfair practice proceedings a review of the arbitrator’s decision.” Id. at 650. Consequently, collateral estoppel does not apply, and the trial court therefore erred in concluding that the decision in Case No. 41 divested the arbitrator of jurisdiction.3
When an arbitrator interprets a collective bargaining agreement, the arbitrator decides a factual question of the *372parties’ intent. Williamsport Area School District v. Williamsport Educ. Ass’n, 686 A.2d 885 (Pa.Cmwlth.1996). In finding that the nurse assistant RNs’ work was substantially the same as that of the certified nurses, with the exception of a few hours of classroom instruction on Growth and Development, the arbitrator stated:
The connotation, assistant nurse, in this matter seems to be a misnomer. The record establishes the fact that said nurses in question are not assisting in the true sense of the word but are functioning and performing their duties on a one per one basis in all six schools in an independent fashion.
Under direct examination the certified nurses made it explicitly clear that they had no supervisory responsibilities in regard to the assistant nurses, that when they met once a month it was a mutual relationship without any specific director or direction.
By virtue of the fact that said nurse assistant, registered nurses are members of the Bargaining Unit representing professional employees of the District negates the District[’]s contention that said employees are para professionals and not entitled to all rights and benefits provided other professional employees of the District. One of the three assistant nurses, registered nurses possesses a BS degree in nursing and is presently being denied her professional status that the District says is a prerequisite for professional placement.
Certified Record, Arbitrator’s Decision, pp. 10-11. The arbitrator’s findings that the duties of the two positions are substantially similar and that the nurse assistant RNs are covered by the CBA were based on his interpretation and the evidence.4
The School District argues that the nurse assistant RNs are neither professional employees under Section 1101(1) of the Public School Code of 1949 (Public School Code), Act of March 10, 1949, P.L. 80, as amended, 24 P.S. § 11-1101(1), nor “school nurses” under Section 1401(8), added by Section 2 of the Act of July 15, 1957, P.L. 937, 24 P.S. § 14-1401(8);5 that *373while they may provide the same nursing services as the certified school nurses, they may not perform classroom teaching under the Certification and Staffing Policy Guidelines of the Department of Education; and that granting them the same rights, benefits and protections available to professional employees directly conflicts with the Public School Code. It relies upon Section 703 of the PERA, 43 P.S. § 1101.703, which provides that parties to a CBA shall not effect or implement any provision in a CBA if doing so would violate or be inconsistent or in conflict with any statute. The parties agreed “to abide by applicable laws including the Public School Code of 1949, as amended.” Article IV, Section 1 of the CBA; R.R. at 213a.
In School District of Township of Millcreek v. Millcreek Educ. Ass’n, 64 Pa.Cmwlth. 389, 440 A.2d 673 (1982), the Court held that the purpose of a unit clarification procedure under the PERA is to determine whether specific job classifications are properly included in the bargaining unit based upon actual job functions and that Public School Code provisions are not dispositive of employee status under the PERA. The Court concluded that the distinction in the Public School Code between permanent and substitute teachers is merely one factor to be considered in ascertaining whether the two groups share a community of interest.
The School District agreed to include the nurse assistant RNs in the bargaining unit, and it concedes that they are “professional employees” under the PERA.6 The School District fails to elaborate on how or why it believes the award violates the protections provided by the Public School Code. Cf. Mifflinburg Area Educ. Ass’n v. Mifflinburg Area School District, 555 Pa. 326, 724 A.2d 339 (1999) (holding that award denying credit for past service violated Section 1142 of the Public School Code, 24 P.S. § 11-1142, setting forth minimum teacher salaries and increments, and did not derive its essence from the agreement); Greater Johnstown School District v. Greater Johnstown Educ. Ass’n, 804 A.2d 680 (Pa.Cmwlth.2002) (holding the agreement that substitutes had no ñght or claim in seniority calculation, salary schedule placement or accumulation of sick leave invalid).
The trial court’s scope of review of the arbitration award was limited by the essence test as enunciated in Cheyney University. That review was limited to determining whether the issue before the arbitrator, as properly defined, was within the terms of the CBA, and if so the award will be upheld if the arbitrator’s interpretation can be rationally derived from the CBA. The trial court could vacate the award only if it “indisputably and genuinely” lacked foundation in or failed to logically flow from the CBA. The arbitrator’s conclusions here that the grievance was arbitrable and that the nurse assistant RNs are covered by the CBA were rationally derived from the terms of the CBA. As such, the trial court exceeded its limit*374ed scope of review in vacating the award, and the Court must reverse its order.
Judges COHN JUBELIRER and LEAVITT dissent.ORDER
AND NOW, this 20th day of February, 2007, the Court reverses the order of the Court of Common Pleas of Indiana County and reinstates the award of the arbitrator.
. Under Article III, Section 3 of the CBA, the fifth and final step of the grievance procedure is a final and binding arbitration award.
. The trial court also concluded that a lack of the arbitrator’s subject matter jurisdiction would be a basis for granting judgment notwithstanding the verdict under Section 7302(d)(2) of the Uniform Arbitration Act, 42 Pa.C.S. § 7302(d)(2), which provides that “a court in reviewing an arbitration award ... shall ... modify or correct the award where the award is contrary to law and is such that had it been a verdict of a jury the court would *370have entered a different judgment or a judgment notwithstanding the verdict.”
. The trial court also suggested that the arbitrator’s decision was barred by technical res judicata. An application of technical res judi-cata requires identity of (1) the things sued upon or for; (2) the causes of action; (3) the persons or parties to the action; and (4) the quality or capacity of the parties suing or being sued. J.S. v. Bethlehem Area School District, 794 A.2d 936 (Pa.Cmwlth.2002). Because the unfair labor practice proceeding before the Board and the arbitration proceeding involved separate causes of action, technical res judicata does not apply.
. The dissent cites Town of McCandless v. McCandless Police Officers Ass’n, 587 Pa. 525, 901 A.2d 991 (2006), to support its position that a plenary standard of review should apply to this case because "the arbitrator's jurisdiction over the grievance did not require fact-finding, nor an interpretation of the CBA,” op. at 377, and that under this plenary standard of review the arbitrator’s decision is not entitled to deference. The McCandless Court only reaffirmed the plenary standard of review of grievance arbitration appeals under the Act of June 24, 1968, P.L. 237 (Act 111), 43 P.S. §§ 217.1-217.10, which applies to police and fire personnel. The Supreme Court did not extend the plenary standard of review to grievance arbitration appeals under the PERA, and the dissent fails to cite any authority whatsoever for doing so in the present case. Moreover, under McCandless the plenary review standard governs the preliminary determination of the arbitrator's jurisdiction "unless ... that preliminary determination itself depended to some extent upon arbitral fact-finding or a construction of the relevant CBA.” Id., 587 Pa. at 540, 901 A.2d at 1000.
In applying the doctrine of collateral estop-pel, the dissent considers only the Board’s decision in Case No. 41 and ignores the Board’s decision in Case No. 61, which recognized that "the same conduct may constitute both a claim of violation of a contract and a statutory duty to bargain.” R.R. at 433a. The Board clearly explained that ”[i]n directing arbitration of the Union’s grievance, the Board does not address the merits of the District’s claim of arbitrability." Id. at 431a (emphasis added).
. Section 1101(1) of the Public School Code provides that ”[t]he term 'professional employe’ shall include those who are certificated as teachers, supervisors, ... dental hygienists, visiting teachers, ... school counselors, child nutrition program specialists, school librarians, school secretaries ... and school nurses.” Under Section 1401(8), a "school *373nurse” means “a licensed registered nurse properly certificated by the Superintendent of Public Instruction as a school nurse who is employed by a school district....”
. Section 301(7) of the PERA, 43 P.S. § 1101.301(7), defines a "professional employe” as "any employe whose work: (i) is predominantly intellectual and varied in character; (ii) requires consistent exercise of discretion and judgment; (iii) requires knowledge of an advanced nature in the field of science or learning customarily acquired by specialized study in an institution of higher learning or its equivalent; and (iv) is of such character that the output or result accomplished cannot be standardized in relation to a given period of time.”