Youth football / training

[Green Breath]

A question for debate. Not CIS specific - but considering that the season is still a few months away and most of the recruiting is finished I figured it wouldn't be out of bounds.

What kind of training should Pee Wee and Bantam aged kids who are serious about the game be doing during the off-season? I have my own sons (13 - 15) who have been training with Marvin Pope here in Calgary since their minor football seasons ended last year. They have been going 4x per week and the results are obvious - yet a lot of folks seem to think that they shouldn't be training as hard as they are considering their youth. Their biggest point concerns stunting growth.

If there are any strength / conditioning coaches, kinestheology majors out there who want to shed a little light on the subject?

They enjoy the training and tend to do a lot of field work and some weights (low weight / high reps.) A lot of these kids, the 12 - 15 year old players in particular, have shown a pretty dramatic improvement in size, speed, and strength. Does this come at a price?