169.370.  Obligations chargeable to general revenue fund — alteration of existing rights prohibited. — 1.  Interest charges payable, the creation and maintenance of reserves in the general reserve fund and the payment of all retirement allowances, refunds and other benefits and expenses are hereby made obligations chargeable against the general reserve fund and not of the school district, and the moneys placed in the general reserve fund shall not be diverted or used for other purposes.

  2.  No alteration, amendment or repeal of sections 169.270 to 169.400 shall be deemed to affect the rights of members of any retirement system established thereunder with reference to deposits previously made, or to reduce any accrued or potential benefits to those who are members at the time when such alterations, amendments, or repeal becomes effective or to reduce the amount of any retirement allowance then payable.