I think the culture is different up here in Canada... pretty much everyone starts drinking before the end of high school, since the drinking age is 19.
I agree with everyone else though, you gotta just be sensible about it and not over-do it. There are also some dumb kids at my school (keep in mind there are only 60 kids in each grade/year, so only 60 seniors, 60 juniors, etc). One girl pre-drank at a guy's house, then showed up for the school dance (this is a typical thing do to). But apparently this was the girl's first time drinking, and she drank waaaay too much vodka, and passed out as she was walking up the school stairs. They had to call an ambulance, and she was suspended from school for three days (since it was on school property).
Our semi-formal was held up the road from our school (which is in downtown Toronto) at this club that you rent out. So typically kids will bring bags with booze to leave somewhere outside, and then pick them up and take them to the after party. But the school went around snooping for bags after the doors closed, and any bag they found with alcohol AND ID, they pulled those dumb kids out, and then they also got suspended for a few days. On the flip side, they were really lax about kids who had drank and were inside, and the first day of school after the semi, the teachers there would tease us about "looking suspicious" and having "too good of a time" hahaha.