Children under the age of 8 must be secured in a car seat or booster seat in the back seat. Children under the age of 8 are required to be secured in a car or booster seat.Beginning January 1, children under age 8 must be properly buckled into a car seat or booster seat, and ride in the back seat. Children under 2 years of age shall ride in a rearfacing car seat unless the child weighs 40 or more pounds OR is 40 or more inches tall. Age and Height Requirements: Children must be in booster seats until they're eight or 4 feet 9 inches tall. Children under age 8 must ride in the back seat in either a car seat or a booster seat. California law requires a child to be 8 years old to ride in the front seat. According to California law, you should secure children under the age of two inside a rearfacing car seat. California law does not address graduation time from a five point harness to a booster seat. Also fill out the registration form when you buy your car seat.