There is created a health insurance fund for public school employees. The fund shall be available without fiscal year limitations for premiums, subscription charges, benefits, and administration costs. The amounts contributed by the state or from federal funds pursuant to this subpart shall be credited to such health insurance fund. All other income, including the income derived from dividends, premium rate adjustments, or other refunds under any such contract or contracts, shall be credited to and constitute a part of such fund. Any amounts remaining in such fund after all premiums or subscription charges and other expenses have been paid shall be retained in such fund as a special reserve for adverse fluctuation. The commissioner shall be the custodian of such health insurance fund and shall be responsible under a properly approved bond for all moneys coming into the fund and paid out of the fund as may be required to be paid to any contracting qualified entity under any contract entered into pursuant to this subpart and to cover administrative costs.