Almost all minors under the age of 18 are subject to California's child labor protections. All minors who have not graduated high school or been awarded a certificate of proficiency, must have a valid work permit.Children ages 12 and 13 can only work on days when there is no school. The law allows them to work up to eight hours a day and no more than 40 hours a week. California follows a state minimum wage law. All minors are permitted to work up to eight hours per day when school is not in session. Permissible and Prohibited Occupations. However, employers of any minor must obtain and keep on record proof of the child's age. All minors under the age of 18 must have a permit to work in the State of California. The general rule is that the legal working age in California is 14-years-old, but anybody under the age of 18 must have a work permit.