California Code, Education Code - EDC § 17531

(a) Except as provided in subdivision (b) of this section and Section 17532, the amount of classroom space leased pursuant to this article in any schoolsite during normal school hours shall not exceed 45 percent of the total classroom space of that school, and in no event shall the leased classroom space in the school district during normal school hours exceed 30 percent of the district's total classroom space in operating schools.

(b) The governing board of a school district may, upon a two-thirds vote, enter into lease agreements which exceed the 45 percent limit per school upon making a finding that the leases are compatible with the educational purpose of the school.  The board, however, shall not exceed, pursuant to this subdivision, the 30 percent limit of classroom space for the entire school district.

(c) The provisions of this section shall not apply to agreements for the lease of classroom space entered into by districts on or before March 4, 1981.