The American Academy of Pediatrics (AAP) recommends that children use a forward-facing car seat with a harness system until they outgrow the height and weight limits specified by the car seat manufacturer. Once a child exceeds these limits, usually around the age of 4 to 7, they can transition to a booster seat. However, it is important to follow the specific guidelines provided by the car seat manufacturer and consult local regulations for precise requirements in your area.