Applications for leaves of absence shall be given preference, according to the years of service since the previous sabbatical leave of the applicant, and in accordance with regulations adopted by the board of school directors.

No school district shall limit the number of leaves of absence granted in any school year to less than ten per centum (10%) of the number of persons eligible for such leave of absence regularly employed in such district. Schools which have a staff of seven (7) or less teachers shall be permitted at least one leave of absence each term.