In the US, the "big" high school events seem to be things like Homecoming and Prom, and they are somewhat exclusive (usually the upperclassmen participate more). In Japan, it's been my experience that the "big" school events are the "Bunkasai" (Culture Festival) and "Taikusai" (Sports Festival). These events involve the entire student body in various ways, culminating on the festival days, which happen to be last weekend and this weekend for my school this year.

In this little slide show, you see the drawings the students did of their homeroom teachers. The numbers you see in the pictures are the year & grade of the students - ie: 3-1 = third year, class number 1. Which translates to class 1 (out of 8) of the senior class. I wish you knew the teachers in the pictures - it would make them even funnier. My favorite is the one of the two teachers sitting at a table in a "snack bar" (not like those in the US - Japanese snack bars are basically places where men pay for female employees' (hostesses) drinks so that they'll keep them company).
Note - the teachers in that picture are both male...

You can click on the slide show to see the pictures & comments in my Picassa web album.