Children should stay in a booster seat until they're at least four feet nine inches and reach their 8th birthday. Texas law requires all children younger than 8 years old, unless taller than 4'9", to be in the appropriate child safety seat system.In Texas, the law requires children to remain in a booster seat until they reach the age of 8 years or 4 feet 9 inches in height. Texas Child Passenger Safety Laws. Your child will no longer need a car seat if they are at least four feet and nine inches, eight years of age, and the vehicle seat belt fits them properly. Texas law requires that young children use proper safety equipment when riding in motor vehicles to protect them in the event of an accident. If they're between ages 1 and 3 and weigh more than 20 pounds, children still have to be in a child restraint. There is no law in Texas specifies when a child can sit in the front seat. Seat Belt: Children who are too big for booster seats yet still below 17 years of age must wear a seat belt as per Texas law. Kidmoto Car Services with Safety Seats in San Antonio.