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. No school district shall be required to change its graduation schedule or require graduating students to return to school after graduation to make up class days lost due to severe weather conditions or, in the school year 1979-1980 for situations beyond the control of the school district as a result of major construction and renovation to the school building. No district which makes a bona fide effort as determined by the Secretary of Education to provide one hundred eighty (180) days of instruction for graduating students shall receive less subsidy payments or reimbursements than it would otherwise be entitled to receive on account of the school year because of the provisions of this section. Unless otherwise provided by this act, the board of school directors in any district or joint board may keep such other schools or departments as it may establish open during such time as it may direct.

Twenty days of actual teaching shall constitute a school month.