Cal. Ed. Code § 16065
Notwithstanding any provision to the contrary after June 28, 1955, at the time the board makes an apportionment, the board, with the approval of the Director of General Services, shall, pursuant to this section, fix the rate of interest to be paid by the district on the sum apportioned to it. The board shall compute the average of the rates of interest which the state pays upon the state school building bonds, authorized by Article XVI, sold at the three sales of state school building bonds occurring immediately prior to the apportionment, or, if the board so determines, at all of the sales of the bonds occurring in the two years immediately prior to the apportionment, giving effect to the price at which the state school building bonds sold at the sales, and the premium, if any paid, thereon. The average rate shall be adjusted to the next highest one-tenth of 1 percent to cover the cost of sale and issuance of the bonds and costs of administration. The adjusted average rate shall be the rate paid by the district on its apportionment, and shall be compounded annually through the 30th day of June of each year.
Ca. Educ. Code § 16065