i was into the bodybuilding scene all 4 years in college and actually competed in the ONBF Mr. Natural Ohio back in 2006 taking 1st in under 24, novice, and 2nd in lightweight and i'd never train without it. just make sure they're drinking lots of water to see maximum benefits and avoid dehydration. gallon per day is the recommendation, just fill an old milk jug and make em finish it over the day. definitely noticed increases in strength and size, but that's NOT in absence of a strong diet plan and solid workout routine, which are SIGNIFICANTLY more important. if they want anymore info, i'd be glad to help, though i'm surprised their coach is recommending it. not too often you see coaches sticking their necks out on supplements cause if anything happens to them on the field, i GUARANTEE it will get the blame and the coach will be held responsible. i wouldnt bother spending the money on the fancy creatine combo mixes, just get some cheap creatine monohydrate from www.bulknutrition.com and avoid GNC like the plague if you wanna save money. also, i didnt notice they're 15, not sure how you feel about supplements and their age, not that i have any reason to say it's a bad idea, just never keen on recommending things for kids.