I'm no doctor but I have had literally a lifetime's worth of ear problems so take this for what its worth.
A few decades ago they believed putting tubes in the ears was the panacea for kids with persistent ear infections, most doctors including ENTs still subscribe to this. As you know, the reality is that the operations aren't foolproof and a number of us collected a fair amount of scar tissue on the eardrums in the process. Moreso than if the eardrums were allowed to (painfully!) rupture according to some ENTs. The problem this creates is some degree of hearing loss with the loss of flexibility to the eardrum.
As long as his eardrums are properly healed, that
should be OK for diving. The problem will probably be more with whether his ear infections continue (i.e. fluid) and if his eustachian tubes allow him to clear his ears. I'm cursed with "oddly shaped" eustachian tubes (which you are supposed to outgrow in adolescence) that seem to make infections more common and can make clearing difficult but by no means impossible.
I was told by a (non-diver) ENT that I wouldn't be able to clear my ears and so wouldn't be able to dive, my (diver) family physician said to try it and see. Long story short, I just have to work a little harder at it, and I can dive just fine. I also stay on top of any ENT issues and my doctors office has this labelled on my chart so I don't have problems getting in to see him if I need to knock down an infection in the early stages.
He should still see a doctor, even an ENT, but make sure they are either well versed in hyperbaric medicine or at least that they dive themselves. If he answers the medical questionaire honestly (and some don't!) his instructor and doctor will at least be on the same page and hopefully the instructor will be able to spend extra time working on this with him if need be.
Good luck!
http://www.slcent.com/eustachian.html
