Muscle and Whey protein

My 17 year old son is fairly skinny (125 lbs, 4 feet 9 inches), and he has been working out.  He has seen some results, but he is not gaining much weight nor is he getting "big" (a little cut but not really bigger and stronger and more muscular).

A trainer suggested that he buy whey protein powder and have a shake an hour? before and right after he works out?

First, is this healthy?  Is this a good way to get the most out of workouts, and to gain some weight without getting fat.  If so, when should he have the shakes?  Also, how long should he have them for?  Should he take them every time he works out?  After a few months, if he stops having the shakes, will the results last without continuing to have them?  Separately, will his body rely on them in the future to build muscles?

Lastly, is one powder better than another?  Where can I get good whey protein?

[marissposa]

I don't think your son needs a shake per se.  He should be bulking up on protein and calories.  It doesn't really matter which form.    I always think the less processed food the better, but  if your son prefers powdered protein, it is not really dangerous, it just has a lot of unnecessary additives and I find them difficult to digest.  It is important to eat some sort of protein within a half an hour of working out to repair any muscular damage that has occurred. Also drink a lot of water and make sure you are getting enough calcium and potassium.
Bulking up is not only a matter of what you eat or how much you lift, but also the way in which you do it.  When lifting for bulk  fewer reps with more weight is better,  and you want to totally burn out the muscle, lift until you don't think you can do any more, than do  1 more, rest,  do as many more as you can, rest,   do 3 more, rest, 2 more rest, 1 more.  Load on so much weight that you can only do about 15 or 20  the first time around.  After time you will have to increase this.  If you work out every day, the next day let the muscle groups you worked rest and do a different area.
The Most Important Thing  is to protect your spine when lifting.  Hold you abs tight, and lift your pelvic floor (do this by tightening the muscles you use to stop the flow of urine) and relax your jaw and neck.
Let us know how it goes or if you and your son have any questions.

[RockRose]

John,  can you recheck what you wrote as his height and weight?  I don't think that's what you meant to say.