The whole notion of growth being stunted by weight lifting is
a myth. It didn't stunt the growth of Shaquille O'Neal, David
Robinson, Karl Malone, Michael Vick, etc. They all started
lifting in their early teens, and all have gone on to be well
over 6' tall and star in professional sports.

Dave Draper and Arnold Schwarzenegger started lifting very
young and both are 6'1“ or taller. Lou Ferrigno started
working out at 14 years old at the height of 5' 9” and grew to
6' 5" - taller then anyone in his family!

So the answer is no, weightlifting does not stunt height growth, or
any other kind of growth, for that matter. There is no scientific
evidence to support such ideas and, in fact, books such as the
Russian, School of Height, suggest that weight training may
stimulate growth. The latest weight training studies done on
teens showed only positive effects.

Congratulations to your son on starting a weight-training program at
so young an age! Not only will proper weight training not stunt your son's
growth, it will allow him to grow up with stronger muscles and bones,
along with a healthy lifestyle. It certainly will benefit his football game,
too, not to mention any other sport that he tries.

First off, weight lifting does not stunt your growth. This is a myth. This myth stems from the beleif that weight lifting can damage the epiphyseal growth plates on the long bones of the body…this is the region on bone where growth ocurrs.

If you lift in good form, allow for adequate rest, and avoid heavy lifting, you should be fine. Your doctor gave good advice: moderate training using a range of 8-12 repetitions to fatigue in good form is recommended by the American College of Sports Medicine for young people in your age range.

Be patient. Your body is changing…and with those changes comes hormaonal changes and increases in muscle mass. Your body will respond to training, even at the rep rang of 8-12, and wil prepare you for heavier lifting as you mature and reach the age of 18.

Lifting weights doesn't stunt anyone's growth. There is no evidence to back this belief at all in anyone. It was started as myth like so many other “facts” going around. It seems that people simply want to view bodybuilding in a negative light so many of these un-truths popped up in justification of that. The only reasons most pre-teens are advised to avoid lifting is due to; poor overall body strength, the risk of injury and the simple fact that no pre-teen is producing enough hormones to see much at all as far as muscle growth from a serious lifting routine.

One of the biggest myths about weight lifting is that it stunts your growth. No studies have ever been shown that lifting weights stunts or inhibits growth. But, as with any exercise program, if you do too much too soon, physical problems can occur no matter how old the person doing the exercise is. The most important aspects when training as a child are supervision, exercise technique
As a teen, you may gradually progress to heavier weights with lower reps, around 10 per set.
If you are a normal teen, somewhere between sedentary and athletic, you should undertake a more intense program. As a beginner, you want to work out three times a week, doing 10 repetitions per set, and around 4 sets per exercise. Use 3 to 4 exercises per body part. Try to stay away from compound movements (using a number of muscles, i.e. clean & jerk, bench press, deadlift), as their execution is very technical, and you can injure yourself if you are not under proper supervision. Once you become more advanced, you may wish to switch to a split-routine, in which you train different body parts on different days.