1. That the board of trustees or other officer or officers in charge of every institution in the state of Missouri which is supported in whole or in part by public funds, and who are required to purchase coal for fuel purposes in the operation of any such institution, shall be required to purchase and use coal which is mined in the state of Missouri or an adjoining state, if the cost of coal mined in the state of Missouri or an adjoining state is not greater than the cost of coal mined in any other state or states, including the cost of transportation.

2. The term “institution” shall be construed to include all institutions supported by public funds of the state, but shall not include municipal corporations, political subdivisions or public schools.