No person shall knowingly drive a bus within the City of San Diego which is transporting any public or private school pupil who is enrolled in kindergarten or any of grades 1 to 12, inclusive, to or from a public or private school, unless every such pupil is seated in a seat.
Source:
Section 21700.5, https://leginfo.legislature.ca.gov/faces/codes_displaySection.xhtml?lawCode=VEH§ionNum=21700.5..