May I suggest asking for a sit down meeting with the principle and / or Superintendant. Explain the reasons you are wearing it and bring some documented comments of students and STAFF (ESPECIALLY staff comments) to the meeting. If you CAN get a mini video camera into school or have a digital camera with a "mini movie setting", hold the camera (down at your side and out of view) as you walk between classes. This may help to get the taunting caught on tape. Ask what can be done to stop the harassment as it SURELY would not be tolerated if it were another gender / cultural issue.

How can you stop them from pulling it off? Wear suspenders on the kilt (under your shirt, so they're not visible).

Bottom line... the harassment probably WON'T stop completely. You're different and in High School... kids like to "belong" and follow the herd. If you go against the grain, they'll make fun of you for it. Just remember this... 10 years from now, you'll be glad you did it and they'll be ashamed they made fun of you. It also shows your level of character and class (and theirs).