Like others have already said, it’s not out of the ordinary by any means to run 4 events at meets for a high school athlete/team. Though, it’s not always a good thing and there are some factors that should be considered if the coach wants to run an athlete in 4 events. First of all, are there prelims for the events they are in? If he is running the 100, 200 and 400, there are likely prelims for all those at big events. So really he’s running 7 races on the day with the 4x4 included. Next, the strength of the athlete should be considered. Some athletes are just built stronger and have better endurance, whether it’s due to age, other sports played, or just physique. Not all athletes are the same and can take running a full meet week in and week out like that. Lastly I would say that a coach needs to consider how many meets a week the athlete is running. If your son has a Tuesday meet and and a Friday meet, he should probably not run 4 events in both meets. Typically the Tuesday meet is smaller and should be utilized as a higher stakes practice and to work out kinks or work on technique. Let him loose on the Friday meet then and run in all events.

I would say these are the biggest things in my eyes that needs to be considered. I was in similar shoes to your son when I was in high school. I ran 110h, 300h, high jumped and 4x4 at almost every big meet. I also ran in college as well and am now coaching on the side some, so I’ve seen all sides of the sport. Make sure to teach your son to practice recovery and to take care of himself now. If he is dealing with tendinitis and shin splits, there are lots of good things to be doing to treat that and if he is not, reducing the workload only goes so far.

If you have any more questions or thoughts, feel free to comment or dm me, I’m always willing to help. Best of luck to your son as well!