Contractors shall arrange for the exchange of items, allowing pupils or boards of education an exchange price as liberal as granted on the same items to any city, county, or state in the United States, like conditions prevailing. The exchange privilege shall extend through one entire school year. Nothing in this article is to be construed as preventing the use of supplementary books, instructional materials, or learning technologies provided they do not displace the adopted items, nor the use of more advanced items in such schools as may be ready for the same. On or before the first day of July, one thousand nine hundred ninety-four and thereafter, the state board of education is authorized to approve any depository or depositories, either public or private, to serve any county or several counties, whose purpose includes, but is not limited to, offering the savings and services generally associated with local distribution of textbooks, instructional materials, or learning technologies or any combination thereof, to counties and schools.