EarDrums

Your son should definitely be wearing hearing protection, always. Full stop. Hearing doesn't come back once damaged. There are all sorts of options with this. I've used Shure, and Drumeo EIM's, plugged into a metronome app called Tempo. Apparently Vic Firth makes pretty good over-ear headphones, hell even good old fashioned foam plugs will work in a pinch (and you can keep time visually with most metronomes).

Buy the drumeo iems. They are inexpensive and of decent quality

Just to add some perspective. I have used 215s for years, I got some kz zs10s about 4months ago and found they were far too bassey and had some high freq sibilence... plus the cable is pretty cheap, has a poor fit over the ear. I got some drumeo eardrum black editions a week ago, (black friday deal) and they sound better (much flater curve) for drumming. The fit is better and the cable is 100x better than the KZ. Overall the sound quality for drumming and general music i found slightly better than the shures (kz was good for edm, but bad for drumming and metalcore). Time will tell regarding durability... shures have lasted ages, but quality of eardrums seems good.

I got a free pair when I signed up for Drumeo and I feel like I overpaid for them if I’m honest

I mean, I got mine for free for signing up so I may be bias, but for the cost they are not bad. I got decent isolation with the medium insert. Your ears just might have just developed a way that just doesn’t work for you. They are OK IEMs. No where near the best but far from the worst. Anyway, I switched to Alclairs and won’t ever look back. For the cost, longevity and hearing protection of customs molded IEMs outweigh the drop ins any day for a drummer.

It might just be my ear shape… but coming from some 20 year old shures to the drumeo IEMs, it was definitely an upgrade… BUT after trying all the switchable ear inserts, I found the best isolation fit with the standard ones the came with (again, probably an ear hole shape thing) And isolation is great with these… I was able to turn EVERYTHING down to save my ears for rehearsal and shows… Yes, the sound is flat (not a lot of bass) and I wish the good quality replaceable cable was much longer (nothing a 6-13’ aux extension from Best Buy hasn’t remedied …… I’m not a fan of a wearable pack- I like to go right into a mini mixer on my left side )

I got the Drumeo InEars on sale for 100 bucks and I‘m very pleased.