This is tough.
1) School is the most important thing you will do in to prepare you for your life ahead.
This kilt thing may be to much of a distraction right now.
Pants may be your best bet until you go off to College.
There are many college aged members on this site who will tell you about kilted at that level.
OR: when you are not in school or studying; go to the gym and the martial arts studio. then a little intimidation goes a long way.
When students try to lift your kilt or pull it off, loudly say: Who is the Queer now, trying to take a boys clothes off?"