A school term begins and ends on the dates fixed by the governing body of a school district. A school term shall include not less than 180 days in session unless, with the approval of the commissioner,
(1) a day used for in-service training of teachers is substituted for a day in session, up to a maximum of 10 days;
(2) an “emergency closure day” is substituted for a day in session because of conditions posing a threat to the health or safety of students; or
(3) the school board adopts a different school term that includes at least 740 hours of instruction and study periods for pupils in kindergarten, first grade, second grade, and third grade and at least 900 hours of instruction and study periods for pupils in grades four through 12 if the commissioner finds that the school board has submitted an acceptable plan under which students will receive the approximate educational equivalent of a 180-day term.