Im probably just gonna turn the tables and make them feel uncomfortable.
They already feel uncomfortable; that's why they're doing what they do. Most likely they're envious or simply curious, but don't know how to express it the right way.

My personal advice is twofold:
1) Wear the kilt when you want (without deliberately trying to agitate people) and wear it proud. 100 years ago women were having this fight about pants. You're not doing anything wrong, illegal, or weird, so don't worry about it.

2) Repay their hate, spite, and hurtful actions with kindness, genuine care, and a heart of service. In time you’ll find that if you brush off their rude comments, ignore their attempts to humiliate you, and don’t react angrily, things will probably taper off. Then again, they may not. In either case, don’t lower yourself to their level by reacting immaturely or spitefully.

If there are serious attempts at publicly humiliating you by lifting/pulling down your kilt (not just “playful” teenage banter), I would suggest couple strategies: First, travel in a pack. Surround yourself with your friends to act as a shield of sorts. It’ll be hard for the cowardly bullies to get to you if you’re surrounded by 2-3 friends all the time. Second, seek out sympathetic, understanding faculty (teachers). Friends in high places are not to be underestimated. One or two teachers on your side can make all the difference.

This is slightly off-topic, but it relates, so bear with me a moment. I don’t wear shoes of any kind. Like, ever, anywhere. (Except to Church and other formal events.) It gets me some strange looks, some stranger comments, and even stranger troubles, at times. It isn’t illegal, it isn’t wrong, and while some would argue that it is, it isn’t weird. (A guy with a kilt that comes half way down his calves is weird; not wearing shoes when you don’t need them isn’t. But I digress.)

Really it boils down to the same thing: the social “norm.” Some of us thoroughly enjoy things that go against the social norm, and we’re beaten up for it. You have to stand your ground and act respectful and kind, even when others don’t. Often you have to remind yourself that there’s nothing wrong with what you’re doing (or wearing, as the case may be) because the comments and stares can get to you after a while.

But that’s what friends and places like X-Marks are for, right guys?! Be proud of your kilt and your Scottish heritage, and remember that the others are the ones in the wrong.

Sorry this turned into a small novel, but it really boils my blood to see anyone, but particularly teenagers, harassed for something as trivial as clothing. I hope some of this advice helps, and I wish you the best in your situation.

Joshua