I'm turning sixteen in two months. I play rugby competitively four times a week. Also recently I have begun weight lifting to assist with development and was wondering is whey protein concentrate a good supplement to take in moderate doses to aid development

Yes, it's fine. Basically, it's a concentrated form of milk, it's a natural food, not some weird supplement that will cause your bits to shrivel up.

One scoop after intense exercise is an extremely useful aid to recovery. More than that is a waste.

Ideally, take it with a small amount of carbohydrate to assist your muscles using it most effectively.