Subject to the regulations prescribed and issued by the Secretary of Defense under section
902 of this title, each teacher (other than an individual employed as a substitute teacher) shall be entitled to cumulative leave, with pay, which shall accrue at the rate of one day for each calendar month, or part thereof, of a school year, except that if the school year includes more than eight months, any such teacher who shall have served for the entire school year shall be entitled to ten (or, if such teacher is employed in a supervisory position or higher, not less than ten and not more than thirteen) days of cumulative leave with pay.