Cal. Education Code § 17091

(a) The board shall have authority to adopt rules establishing priorities for the acquisition and leasing of classrooms to those school districts and county superintendents of schools whose pupils will benefit most. The board may make exceptions from the established priorities if it determines that the pupils affected will benefit. (b) If at any time the number of portable classrooms available exceeds the number of those required by applicant districts, as determined by basic loading standards and eligibility requirements, the board may authorize additional portable classrooms to be placed in any school district that agrees to hire an additional teacher for each additional portable classroom placed in the district pursuant to this subdivision. (c) If at any time the number of portable classrooms available exceeds the number of those required by applicant districts, as determined by basic loading standards and eligibility requirements, the board shall authorize additional portable classrooms to be placed in any school district, upon request of the school district, for the purpose of providing licensed child day care programs or recreation or enrichment activities or programs for schoolage children on a schoolsite, unless the surplus classrooms are needed for emergency purposes.