My son has always been one of the hardest throwers in his age group, he's thrown 82 recently as a 14 yr old 8th grader. Our future high school pitching coach reached out to us when he heard we were going to attend his school next year and invited my son to do a weighted ball workout that he's been doing with his high school and travel team pitcher during the month of Dec and Jan. Ill let you know how it goes, its been tough to stay on program we seem to miss 1 or 2 day every week for 1 reason or another but I think its helping. at a minimum it seems hes getting his arm in shape for the spring season about to start down here in Texas like tomorrow. It was interesting when coach pulled out the radar the other day and was getting times for every color ball the intensity really picked up. Everyone complained of being sore the next day, as an aside from a different thread I picked up a marc pro on ebay for about 1/2 cost of a new one and my son used it that night and was only kid the next day that was not sore.
Manage your son closely... Coaches have good intentions but unless they're teaching the correct protocols and the player is following the protocol to the detail you can run into arm issues. Whether it's weighted ball or bands.
Our club baseball program went big on the weighted ball program 2 years ago and disbanded it after only a year. The reason: a few kids hurt their arms and they think it's because the kids started doing their own versions of the weighted ball program, and the program didn't want the risk. Good intentions, but too many young kids without the maturity and discipline to follow the procedures, and they lacked the physical strength to put their bodies in the correct position to execttue the moves. Our baseball program now focuses on dedicated strength training applicable for baseball and long toss. A few of the kids that had success with the weighted ball program now do it as a supplement to their development at another facility where the pitching instructor is dialed into the protocols, arm care, and throwing is his thing (smaller version of Texas B. Ranch or Driveline).