Children under the age of 8 are required to be secured in a car or booster seat. Children under 2 years of age shall ride in a rear-facing 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. According to California law, you should secure children under the age of two inside a rearfacing car seat. Children under the age of 2 must be in a rear-facing car seat unless they weigh 40 pounds or more or are 40 inches or taller. Car seats are either rear-facing or forward-facing. As a rule, children should face the rear of the vehicle for as long as possible. All children under the age of eight must be secured in a car seat or booster seat in the back seat, according to California state law. Under CA law, children under 2 must ride in a rear-facing seat until they weigh at least 40 pounds or are at least 40 inches tall. Children under age 8 must ride in the back seat in either a car seat or a booster seat.