California Code, Education Code - EDC § 17093

The board shall have prepared for its use, performance specifications for portable classrooms complying with Sections 17280 to 17314, inclusive, which are capable of being economically moved, and bids for the construction of which can be solicited from more than one responsible bidder.  The board may from time to time solicit bids from, and award to, the lowest responsible competitive bidder, contracts for the construction or purchase of the number of portable classrooms it deems will be required by eligible school districts and county superintendents of schools during the next 12 months.