Cal. Education Code - EDC § 39860. Section 39860.
(a)
The governing board of a school district may contract for the transportation of pupils attending schools within the district to and from any exposition or fair, school activities, or other activities that the governing board of the school district determines to be for the benefit of the pupils, in this state, and may pay for the transportation out of any funds of the school district available for the purpose.
(b)
The governing board of a school district shall require that any contract for the transportation of pupils under this section shall include the requirement that a pupil shall not be left unattended on a schoolbus, school pupil activity
bus, or youth bus in accordance with paragraph (4) of subdivision (a) of Section 39831.3.