Trick of Treating was never a required thing (I hope). If you wanted to, you went. It was that simple. I think that its still the same in Grade 8. If you want to spend your Halloween night going down streets knocking on doors and getting candy, go for it. Its fun, and I can completely understand your decision.
If you don't want to, because you think you're too old, or you're new to your neighborhood, that's fine too. Instead you could stay home and watch a movie or play video games. It's one of those questions where there isn't a right answer. It doesn't really matter whether or not you go, it's your decision.
To conclude, I think that the answer to the question above depends on the individual Grade 8 the decision is being made about. Whether they want to go out for Trick or Treating or not, it's their choice.