California Code, Education Code - EDC § 49116

(a) While school is in session, an employer shall not employ a minor 14 or 15 years of age for more than three hours in any day, nor more than 18 hours in any week, nor during school hours, except that a minor enrolled in and employed pursuant to a school-supervised and school-administered work experience and career exploration program may be employed for no more than 23 hours, any portion of which may be during school hours.

(b) An employer shall not employ a minor 16 or 17 years of age for more than four hours in any day in which that minor is required by law to attend school for 240 minutes or more, except as follows:

(c) If evidence is shown, to the satisfaction of the authority issuing the permit to work, that the schoolwork or the health of the minor is being impaired by the employment, that authority may revoke the permit.

(d) Nothing in this section shall apply to any minor employed to deliver newspapers to consumers.