At my school there weren't really any groups. When I first came into HS their was a large variance among different groups, but by the time I was in grade 12 most people really weren't in separate groups. People would be friends with people that normally fall into different groups. One thing that really changed though, was that when I first came in, there were almost no drug users, and now (been done HS since June 06) there is a large amount of drug users, and stoners, which when I first entered HS weren't really around.
For me when I first started HS, I had above average grades, but in grade 10 grades dropped and then in grade 11 I failed 2 of 8 courses so I had to pass all 8 in grade 12 to graduate in my year, and not be forced to take a victory lap