All children under 17 years old must be secured in a safety belt or child safety seat, whether they are sitting in the front seat or back seat. Answer: Texas law requires all children younger than 8 years old, unless taller than 4'9", to be in the appropriate child safety seat system.According to Texas law, children under the age of 8, unless they are taller than 4 feet 9 inches, are generally required to be secured in a child safety seat. Children should stay in a booster seat until they're at least four feet nine inches and reach their 8th birthday. Texas Child Passenger Safety Laws. Under Texas law, any child who is younger than age 8 must ride in a "child passenger safety seat system" unless the child is taller than 4 feet, 9 inches. According to Texas law, kids should remain in booster seats until they are at least 8 years of age or are over 4 feet 9 inches in height. The letter of the law is detailed in Texas Transportation Code 545.412. For instance, some states require children to be in a rear-facing car seat until they are at least two years old, while others may have weight-based criteria. (2) transporting a child in a vehicle in which all seating positions equipped with child passenger safety seat systems or safety belts are occupied.