In order to procure the service at the lowest possible figure consistent with proper and satisfactory service, the governing board shall, whenever an expenditure of more than ten thousand dollars ($10,000) is involved, secure bids pursuant to Sections 20111 and 20112 of the Public Contract Code whenever it is contemplated that a contract may be made with a person or corporation other than a common carrier or a municipally owned transit system or a parent or guardian of the pupils to be transported. The governing board may let the contract for the service to other than the lowest bidder.