233.37  Disposal of instructional materials.--Under rules of the commissioner, or rules of the district school board which have been approved by the commissioner, the district school board may dispose of the instructional materials of an old adoption when they have become unserviceable, upon such terms and conditions as will yield their fair salvage value. The Department of Education shall enter into one or more contracts with recycling firms for periodic pickup in school districts of obsolete or unusable materials to be salvaged.