Opinion by
Judge Craig,This case is before us on exceptions taken by the Secretary of Education and the Attorney General (petitioners) to the November 28, 1979 order and opinion of our late President Judge James S. Bowman, which *85dismissed petitioners’ multi-count petition in the nature of mandamus, equity and declaratory judgment against respondent Mount Union Area Board of School Directors. Scanlon v. Mount Union Area Board of School Directors, 47 Pa. Commonwealth Ct. 409, 408 A.2d 555 (1979).
On the basis of Judge Bowman’s opinion, we affirm his dismissal of the mandamus and equity counts, and the count characterized as Declaratory Judgment No. 2, as moot. We also concur in his reasoning and decision that the remaining declaratory judgment count is proper for disposition.
We are unable to improve on Judge Bowman’s concise statement of the factual basis of this contest, which we quote:
The factual background ... is uncontested. During the 1978-79 school term, Mount Union Area School District experienced a strike of its professional employees, during which strike period twenty-two (22) instructional days were lost except with respect to trainable mentally retarded pupils and those pupils who attended a vocational-technical school. Upon termination of the strike, a collective bargaining agreement was entered into. The original school calendar as adopted by respondent provided for pupil instruction to begin September 6, 1978 and to end on June 5,1979. This calendar provided for 180 days of pupil instruction. After settlement of the strike and agreement with its professional employees, respondent on November 21, 1978, adopted a resolution calling for the revision of the original school calendar with these pertinent features: (1) no days already scheduled for Christmas vacation would be rescheduled as days of instruction; and (2) a revised school calendar would not extend beyond June 8, 1979. *86The .original school calendar provided for pupil instruction to end on June 5, 1979. The following day the Department of Education by one of its officials advised respondent in writing of the department’s awareness of the strike and days lost thereby and of the need to afford 180 days of pupil instruction notwithstanding days lost by reason of the strike.
On January 8, 1979, respondent adopted a revised school calendar for the school year, which provided for a maximum 165 days of pupil instruction, the final day thereof being June 8, 1979. Upon receiving notice of the respondent’s revised school calendar, the department promptly advised respondent that it. was not in compliance with the law which the department considered as mandating 180 days of pupil instruction regardless of the disruption of the original calendar caused by the strike. Respondent declined to further revise its school calendar. Hence this suit.
47 Pa. Commonwealth Ct. at 411-12, 408 A.2d at 556-57.
The declaratory judgment count which we do address asserts that Section 1501 of the Public School Code of 1949 (Code), Act of March 10, 1949, P.L. 30, as amended, 24 P.S. §15-1501, mandates a minimum of 180 days of instruction for pupils in each school year. Section 1501 provides:
All public kindergartens, elementary and secondary schools shall be kept open each school year for at least one hundred eighty (180) days of instruction for pupils. No days on which the schools are closed shall be counted as days taught, and no time shall be counted as a pupil session for any activity to which admission is charged. Unless otherwise provided by this act, the board of school directors in any *87district or joint board may keep such other schools or departments as it may establish open during such time as it may direct.
Our decisions on this question are few, and have been ably summarized in the .opinion of Judge Bowman in this case and by the late Judge Kramer in Commonwealth v. Mifflin County School Board, 30 Pa. Commonwealth Ct. 213 (1977). Hence, only brief discussion of those decisions is necessary here.
Root v. Nothern Cambria School District, 10 Pa. Commonwealth Ct. 174, 309 A.2d 175 (1973) was an appeal from a lower court’s dismissal of an equity suit to compel rescheduling of thirty instructional days lost due to a teachers’ strike in the 1972-73 school year. The majority, in concluding that the lower court had not abused its discretion in denying the requested relief, and the dissenters each noted the imprecise procedural posture of the case: The majority stated that “our review might confine itself to jurisdictional and other procedural and technical problems in the litigation”;1 Judge Mencer noted “significant procedural questions”2 while dissenting on the merits; Judge Blatt, though joining Judge Mencer’s dissent, would have dismissed the case, decided August 28, 1973, as mooted by the expiration of the 1972-73 school year.
The issue was next before us in Commonwealth v. Leechburg Area School Board, 19 Pa. Commonwealth Ct. 140, 339 A.2d 149 (1975), a mandamus action within our original jurisdiction to direct that the board reschedule four days lost due to strike activity. In denying the petitioners’ motion for judgment on the pleadings, the majority reiterated the standard of Root, supra:
[Sjchool boards must schedule 180 days of instruction . . . the requirement of 180 days of in*88struction must be adhered to unless it is impossible or impractical to do so for reasons not within the board’s control ... if it is impossible or impractical to provide the number of days required, boards must nevertheless amend their .schedules so as to provide as many days as sound educational practice requires.
19 Pa. Commonwealth Ct. at 142, 339 A.2d at 150-51.
Our next exposition was in Pittenger v. Union Area School Board, 24 Pa. Commonwealth Ct. 442, 356 A.2d 866 (1976), where mandamus issued to compel rescheduling five strike-lost instructional days. Though unanimous in result, our court divided evenly as to the impact of the decision on Root, supra. Judge Mencer, joined by the late President Judge Bowman and Judge (now President Judge) Cbumlish, stated that Root was overruled insofar as it conflicted with the holding in the case at hand; Judge Wilkinson’s concurrence, joined by Judges Rogers and Blatt, expressed that “under the facts presented here, the Board is under a clear duty to modify the previously established calendar. ... [I]t is not only unnecessary to distinguish Boot, much less overrule it, but, indeed, this decision is in entire accord.” 24 Pa. Commonwealth Ct. at 449, 356 A.2d at 870. (Footnote omitted.)
Our latest foray in this area was Commonwealth v. Mifflin County School Board, 30 Pa. Commonwealth Ct. 213 (1977), where the late Judge Kramer, as a hearing judge, denied peremptory judgment directing rescheduling of nineteen strike-lost instructional days. After addressing the foregoing cases, he concluded that Union Area, supra, was not decisional with regard to the vitality of Root and Leechburg, supra, as precedent under Section 1501.
President Judge Bowman, as hearing judge in the case before us, likewise concluded that Root and Leechburg remained undisturbed by Union Area. *89Therefore he decided against petitioners on the declaratory judgment count, which sought a declaration that, as a matter of law, the 180-day requirement of Section 1501 is mandatory, not discretionary in terms of “sound educational practice ’ ’ or otherwise.
Because we have not had, until now, a majority view as to the impact of our Union Area decision upon the Root ease doctrine, we have decided to review the declaratory judgment count here, and to sustain the exceptions.
As President Judge Bowman noted, this court’s decisions have not been unanimous; we remark further that any conflict in the decisions is not susceptible of simple articulation. However, we see the need for clarity and finality on this recurring question of considered public importance.
We here hold that the legislature has intended by the language of Section 1501 to prescribe, as a matter of statewide policy, a mandatory minimum number of days on which schools “shall be kept open,” which minimum may not be obviated by other than the impossibility of compliance with that requirement within the terms of the entire School Code.
In this respect, we depart from the opinion in Root, supra, only insofar as it may imply that strike activity or other interruption of instruction categorically modifies the obligation of boards to provide 180 days of instruction for pupils. Just as that duty to keep the schools open is not satisfied by the mere adoption of a complying schedule, it is not relieved by disruptions in the schedule. This view comports with the thrust of the decision in Root that “ [b]oards must schedule 180 days and provide this number . . . [unless] unavoidable cause prevents.” 10 Pa. Commonwealth Ct. at 180, 309 A.2d at 178.
After study of all aspects of the problem, we are unable to conclude that a strike or other activity which *90interrupts or delays an originally adopted schedule categorically constitutes such “circumstances not within [the board’s] control” or “unavoidable cause” as to render compliance with the requirement impossible. Strike activity or other unavoidable delay or disruption of a desired adopted schedule renders compliance under the Code unavailable only when that disruption is so extensive as to preclude the possibility of 180 days of pupil instruction within the statutory school year.
We are buttressed in our conclusion, that Section 1501 is mandatory without qualification, by the language of that section particularly and by reading it against the backdrop of the entire Code.
As quoted above, the statute reads that “schools shall be kept open for at least one hundred eighty (180) days of instruction for pupils.” It continues that, in the accounting of those days, “[n]o days on which the schools are closed shall be counted as days taught.” That language plainly contrasts with the permissive language concluding the section: Boards are empowered to “keep such other schools or departments as it may establish open during such time as [the board] may direct.” (Emphasis ours.)
This contrast is evident not only in Section 1501; the Code is replete with examples of the legislature’s alternate usage of “shall” or “may” so as to differentiate those parameters of the educational system within which all boards must operate3 from those ele*91ments of the educational process which are within the domain of individual boards.4
Particularly supportive of our conclusion are Sections 5205 and 520.16 of the Code, which address situations where, due to war (Section 520) or other unanticipated emergency (Section 520.1), boards may be unable to comply strictly with particular provisions of the Code. Under specified circumstances, these sections authorize boards to effectuate, on a temporary basis, certain departures from the requirements of the Code.
Importantly, however, both of those sections explicitly state that “the provisions of this Act requiring a minimum of one hundred eighty (180) session days . . . shall not be affected” by a board’s election to avail itself of the provisions of either section. Thus, even in the severe circumstances described in Sections 520 and 520.1, the legislature has provided that the 180-day requirement is to remain intact.
Such provisions therefore confirm that the legislature intended the 180-day requirement, to be a threshold parameter of educational policy, with deviation allowed only by the legislature. When other substantial emergencies do not detract from the requirement that the “schools shall be kept open each school year for at least one hundred eighty (180) days of instruction,” we cannot conclude that the mandate is obviated by the superimposition of the right to strike on the traditional educational system.
*92We find still additional support for our conclusion in recent enactments of the legislature bearing on the 180-day requirement. In the Act of June 1, 1977, P.L. 4, known as the Weather Emergency Bill, the legislature, cognizant of the disruption in school calendars caused by severe weather in the 1976-77 school year, provided for 177 days of instruction, which boards should “make every effort” to achieve. In 1979, on the heels of the Three Mile Island (TMI) incident (.which closed schools proximate to the island), the legislature adopted the Act of May 11, 1979, Act No. 1979-7, P.L. , which made allowance for a schedule of 174 days for schools within five miles of TMI and 178 for affected schools beyond five miles from TMI: Had the legislature no,t perceived the requirement of Section 1501 to be mandatory and alterable only by action of the General Assembly, there would have been no occasion or necessity for those actions with regard to the requirement. We should not presume the legislature to have enacted meaningless amendments.
We are aware that strike activity might lawfully continue for such a period as to render the provision of 180 instructional days impossible within the terms of the Code defining the school year; in that event, boards must amend their schedules to comply as fully as is possible within the applicable school year.
This result may indeed be inconvenient to many; however, the conflict of the traditional school schedule with the combined effect of the 180-day requirement and the rights of public employees to strike, is not so much a conflict between parties as it is a conflict in policies with enormous independent impact on the educational system. In this regard we find a judicial policy voiced by the Supreme Court in Ehret v. Kulpmont Borough School District, 333 Pa. 518, 5 A.2d 188 (1939) to be persuasive:
*93The question raised is a most serious one and affects the life of our educational system. To hold as appellee contends would place an unbearable burden throughout the State . .. but if the legislature has so commanded, ... it is not for the courts to determine the wisdom of such policy. The Constitution has placed the educational system in the hands of the legislature, free from any interference from the judiciary save as required by constitutional limitations. We may only, in problems such as this, ascertain the legislative intent.
333 Pa. at 521-22, 5 A.2d at 190.
Although the decision in Ehret, which involved retention of teacher personnel when a department is abolished, was against the appellee teacher, the holding nevertheless left unshaken the stated principle of deference to the legislature in these situations.
Accordingly we will affirm dismissal of petitioners’ counts in equity, mandamus and the count labeled Declaratory Judgment No. 2; we will sustain petitioners ’ exceptions to the dismissal of the remaining count, labeled Declaratory Judgment No. 1; and we will declare as a matter of law that Section 1501 of the Code establishes a mandatory minimum number of days on which the schools enumerated therein shall be kept open for pupil instruction within each school year, not withstanding postponement or interruption of adopted schedules by strikes or other cause.
Order
And Now, this 29th day of April, 1980, the November 28, 1979 order of the late President Judge Bowman, dismissing petitioners’ counts in equity, mandamus and the count iabeled Declaratory Judgment No. 2, is affirmed; petitioners’ exceptions to the dis*94missal of the remaining count, labeled Declaratory Judgment No. 1, are sustained. It is hereby decreed that Section 1501 of the Public School Code of 1949, Act of March 10, 1949, P.L. 30, as amended, 24 P.S. §15-1501, establishes a mandatory minimum number of days on which the schools enumerated therein shall be kept open for pupil instruction within each school year, notwithstanding postponement or interruption of adopted schedules by strikes or other causes.
10 Pa. Commonwealth Ct. at 177, 309 A.2d at 176.
10 Pa. Commonwealth Ct. at 183, 309 A.2d at 179.
See E.g.: Written contracts with professional employees, Section 1121, 24 P.S. 11-1121 (see Gordon v. Board of Directors of West Side Area Vocational Technical School, 21 Pa. Commonwealth Ct. 616, 347 A.2d 347 (1975)) ; Minimum salaries, Section 1142, 24 P.S. §11-1142 (see Wildrick v. Board of Directors of Sayre Area School District, 27 Pa. Commonwealth Ct. 612, 367 A.2d 768 (1976)) ; Prescribed courses of study, Section 1511, 24 P.S. §15-1511 (see Mhret v. Kulpmont School District, infra).
See: E.g.: Establishment of additional schools and departments, Section 602, 24 P.S. §5-502; Kindergartens, Section 503, 24 P.S. §5-503; Consolidation of schools, Section 505, 24 P.S. §5-505; Employment of special teachers, Section 1107, 24 P.S. §11-1107; Leave of absence and salary rules, Section 1154(e), 24 P.S. §11-1154 (e).
24 P.S. §5-520.
Added by the Act of January 14, 1952, P.L. (1951) 1940, §1, 24 P.S. §5-520.1.