there are many exchange that allowing young people to do trading without sending any of documents. but their account will not reach higher limit to deposit, withdraw or else and maybe they are missed something like 2fa or others. you can trying with poloniex, bittrex, cryptopia, nova exchange, alcurex. you can register in all of these exchange and they don't know if you are under 18 years old or not. maybe my suggestion will come to bittrex than others because in bittrex, its simple and easy friendly for new people.