Mo. Rev. Stat. § 171.181
In making purchases, the school board, officer, or employee of any school district shall give preference to all commodities, manufactured, mined, produced or grown within the state and to all firms, corporations or individuals doing business as Missouri firms, corporations, or individuals, when quality and price are approximately the same; provided, however, that any board member, officer or employee of a seven-director school district, any portion of which is located in a county of the first, second, third, or fourth class, selling or providing such commodities to the school district except as provided in sections 105.450 to 105.458 shall be guilty of a class A misdemeanor and shall forfeit his position with the school district.
§ 171.181, RSMo