Sale of school real property for taxes; interest acquired by purchaser

Whenever any school or university real property bought on credit is sold for taxes, the purchaser at such tax sale shall acquire only the interest of the original purchaser in such real property, and no sale of such real property for taxes shall prejudice the rights of the state therein or preclude the recovery of the purchase money or interest due thereon. In all cases when the real property is mortgaged or otherwise encumbered to the school or university fund, the interest of the person who holds the fee shall alone be sold for taxes and in no case shall the lien or interest of the state be affected by any sale of such encumbered real property made for taxes.