Keep doing what you're doing.
Train and don't stop. Don't get lazy, don't miss classes, don't get caught up in all the stupid crap kids tend to when they get into high school (smoking, drugs, alcohol, chasing pussy. etc.) All of those will cause worse damage for a developing youth's brain than getting punched.
And again don't stop. When you get older, you'll be a monster because most people aren't fortunate enough to have decided to train at such a young age, you'll have a gigantor advantage.
Once you hit that right age, you'll be a monster and take as many punches in the head as you want, even then the punches won't hurt as much because your speed, deflection and head movement should be phenomenal, the punches will just roll off with all the training you're going to be doing.
Also when you get closer to your goals, get into the habit of doing neck exercises. It may help you when you finally do take that punch in the head.
Seriously, don't let not being able to compete yet get you down, because there's so many other things you can be doing to train yourself in the meantime to prepare for that.