Section 17D. With the approval of a school committee deductions may be made from the salary of a school teacher of any amount which such teacher may specify in writing to the city, town or district school committee by which he is employed for the payment of premiums for income protection insurance, and upon notification of such approval the treasurer of the city, town or district shall deduct from the salary of such teacher such amount of premium as may be certified to him on the payroll and transmit the sum so deducted to the insurance company providing said income protection insurance. Authorization by a school teacher for such deductions may be withdrawn by him by giving at least sixty days’ notice in writing of such withdrawal to said school committee.