My son's 15. He and his friends had a costume party that weekend instead. This year... 2nd annual Halloween Party. He finally got his costume idea last night (Ghosthunter! Just need a flashlight, jacket, belt and tape recorder... he already has his lines down... "Is there anyone here? Can you make a noise for us?")
I think once a kid gets into high school, trick or treating should be over. I can see still going out and goofing off with friends, but save the candy for the little kids.