There are lots of things that a 14 year old can do. First thing I think that is necessary is some supervision of exercise routine is in order. Make sure that the said athlete/child is following directions given in order to not injure themselves. Proper guidance is key here. Too much excercise is not a good thing, so schedule proper breaks for recovery. Muscles need to recover in order to grow and build.
When you workout, you are tearing your muscles and while in the recovery phase, they rebuild. Hence, the growth of muscle and their development.
Try a small regimine of weight, plyometrics, running, stretching, 30 second goes with a partner, drills, take down to a pin, takedown to win, stand-up drill, hand fighting drill: I.e. What do you do when a wrestler grabs your hands: use it against him or her, try a drill where the wrestler grabs your hand-then say to the wrestler, your objective is to use that hand or arm to gain an advatange (arm drag, russian, arm drag to body lock, arm drag to ankle pick, arm drag re-drag) and position drill as it relates to freestyle/greico is also a good thing
another good thing to do is to look for additional practices: camps and clinics
ask your wrestling coach where to find camps and clinics