California Code, Vehicle Code - VEH § 27304

All vehicles owned and utilized in driver training by a driver training school licensed under the provisions of Chapter 1 (commencing with Section 11100) of Division 5 or in a course in automobile driver training in any secondary school maintained under the Education Code shall be equipped with a seatbelt for the driver and each passenger. Such seatbelt shall comply with requirements established by the department.

It shall be unlawful for any driver or passenger to operate or ride in such a vehicle while it is being operated for the purposes of driver training, unless such person is utilizing an installed seatbelt in the proper manner.