average age of 10 to 17 "Teenage Growth & Development: 11 to 14 Years" "Teenage Growth & Development: 11 to 14 Years" "Teenage Growth & Development: 11 to 14 Years" average age of 10 to 17 "Teenage Growth & Development: 11 to 14 Years" "Teenage Growth & Development: 11 to 14 Years"