Actually I am a little surprised that anyone would be unhappy about this situation, given the guy's obvious talent. He might be missing classes now, and I see that is a definite problem, but there's also the chance that he will make a career of sport. To me, if someone shows special talent in something, they should not be held back.
There is no mention here of his grades suffering as a result. If that is the case then there might be an argument for him taking some time away from volleyball to catch up with his school work.
Personally though, I would think that if he agrees to catch up on any missed work during his own time, there really should be no problem. Maybe he could sit down with his parents and a school representative and jointly come up with a plan that suits everyone.
The best option is really to find a compromise.
Ditching lessons and ignoring the importance of education is not the right answer, and is one extreme - but on the other hand, getting the student to give up a sport they enjoy and are talented at seems like an opposite extreme. Being able to negotiate a routine that works for both his sports and education will obviously be the best resolution to this problem.