Nothing in this chapter shall affect the right of the board of education to fix either by rule or by individual consideration, the payment of salary in cases of absence not constituting sick leave, or to grant sick leave over and above the minimum sick leave as defined in this chapter or allowing days to accumulate over and above those provided for in section 18A:30-2, except that no person shall be allowed to increase his total accumulation by more than 15 days in any one year.
N.J.S. § 18A:30-7