§ 3005-b. Leave of absence for personal illness. The school authorities of each school district outside of a city having a population in excess of one million shall allow each teacher employed by the district sick leave without loss of salary for at least ten working days in any year on account of personal sickness or physical disability; and provided, further, that if any employee does not use the full amount of sick leave allowed in any school year, the amount not used shall be accumulated from year to year and used, if needed, up to a total of not less than one hundred fifty working days. Any accumulation of unused sick leave heretofore granted by such school authorities shall be counted toward the accumulated leave herein provided. Nothing contained in this section shall be construed to authorize a reduction in the amount of accumulated leave granted to a teacher prior to July first, nineteen hundred sixty-five.