How much protein should a 14 year old girl eat a day?

It depends upon how active he is. If he is working out every day or on a sports team, he should be eating 50-80 grams of different kinds of protein.

If he is open to taking a supplement Syntha-6 made my BSN is an Excellent long release protein that is 200 calories per serving, and has 20 grams of protein.