ive read and heard that the only way to mess up your growth plates is by lifting extremly large amounts of weights that you cant handle. for mostly all my excersises im doing 3-4 sets 0f 8-15 reps.
yeah im taking protein shakes right after my workout. i looked into the weight gainer at one time but i heard its crap.
You sound like a smart kid so I think you'll do well, keep reading stuff on here rather than listening to mates at school and you should see great progress