Whenever a portion of the National System of Interstate and Defense Highways is constructed on school land and an interchange is constructed on such school land, the Board of Educational Lands and Funds shall offer such land for sale at public auction in such tracts as the board shall determine and sell it at not less than its appraised value. The sale shall be made subject to the rights of leaseholders, if any, and the leaseholder shall be paid for improvements and the value of the leasehold for agricultural purposes. The sale shall be made in accordance with the provisions of section 72-258.