As used in this subchapter:
(1) “Commodities” means all supplies, goods, material, equipment, machinery, facilities, personal property, and services, other than personal and professional services, purchased for or on behalf of the school district;
(2) “Open market purchases” means those purchases of commodities by any purchasing official in which competitive bidding is not required;
(3) “Purchase” means and includes not only the outright purchase of a commodity but also the acquisition of commodities under rental-purchase agreements, lease-purchase agreements, or any other type of agreements whereby the school district has an option to buy the commodity and to apply the rental payments on the purchase price thereof;
(4) “Purchase price” means the full sale or bid price of any commodity without any allowance for trade-in; and
(5) “Purchasing official” means the board of directors of any school district or a lawfully designated agent of the school district with authority to contract or make purchases on behalf of the school district.