putting together then year end video was the better part of my senior years, and i had great fun with it. it was easier for us because we had a team of maybe 5 people who worked on shooting video of every major event, so we had all the footage at our disposal, and it was all pretty good quality (not just handing someone random a camera during a soccer game). we also took photos of all the events, and took photos throughout the year of everyday school life and faces. to start we came up with a theme for the titles and intro, then as each event was covered, it would be edited as soon as possible. then when we got closer to the end of the year, most of the work was done and we just threw in the last few events (even a talent show that happened that same week it was presented).
if you're in need of some ideas, for our intro we had a camera on a wheeled tripod and ran around the hallsof the school for awhile, and people in the halls would look and wave as we passed. it started at the front entrance and ended going out the same doors (i guess symbolizing the high school career in ways). had the opening credits come up during it and sped up the footage to fill however long of a space we had. set it to some sappy music, i believe it was U2's "with or without you". feel free to modify or build on this idea if you wish.
as far as music choices, pick songs that aren't gimmicky or corny. and keep in mind, if you choose songs that you like a lot, you'll likely end up hating them after editing and hearing them 238942789472 times. just pick a few songs that match the content but fit around a central theme.