Operators 18 years of age and older:
You are not required to have an ATV Safety Certificate, but for the safety of the rider, it is recommended.
Operators ages 14-17:
You must possess an ATV Safety Certificate or be supervised by an adult with an ATV Safety Certificate.
Ages 13 and under:
You must be directly supervised by a parent or guardian or an adult authorized by the parent or guardian. If you do not have an ATV Safety Certificate, you must be supervised by an adult with an ATV Safety Certificate.
OHMVR Frequently Asked Questions (ca.gov)
ALL RIDERS UNDER THE AGE OF 18 WILL BE CHECKED FOR ATV SAFETY CERTIFICATION DURING THE REQUIRED DRIVER/RIDER MEETING!!!!