Children who have outgrown their forward-facing car seat with a harness should be secured in a belt-positioning booster seat with the vehicle lap and shoulder belt. In Pennsylvania, children are required to sit in a belt-positioning booster seat until 8 years of age. Children should remain in the booster seat until the vehicle seat belt fits the child correctly. Learn the 5-steps for correct seat belt use. TIPP: Elementary School – Booster Seat Basics / Vehicle Seat Belt Basics