Cal. Educ. Code § 39806

In lieu of providing in whole or in part for the transportation of a pupil attending the schools of a district, the governing board may pay to the parents or guardian of the pupil a sum not to exceed the cost of actual and necessary travel incurred in transporting the pupil to and from the regular day schools of the district. A payment may not be made pursuant to this section unless it will be more economical to make the payments than to provide for said transportation.