The State Board of Education may negotiate and execute contracts with the publishers of textbooks and instructional materials and vendors of instructional technology that allow the State to rent from the publishers or buy outright the books to be used in the public schools, with discretion in the State Board of Education to make rental contracts or purchase contracts as may be to the best advantage of the State. A contract made with a publisher of textbooks may be made so as to divide the payment to the publisher for rental or purchase over a period of three years, but it must not be construed to prevent the State Board of Education from purchasing or renting additional books as necessary. If the State Board of Education decides to purchase outright the books to be used in the schools of this State, they must be purchased at the lowest possible prices and, so far as existing contracts for state-adopted books shall permit, pursuant to competitive bidding.