In my high school, we have this thing called a Senior Honor Pass. It's basically a student ID card that says Honor Pass on it, and basically it gets you out of your free periods. So for example, here's my schedule for my senior year.
1. Study Hall (online college class period)
4.AP English 12
So what the honor pass does is gets me out of my free periods. So first semester my free periods are 1st hour and 5th hour. So I don't have to report to those teachers because I have my honor pass. So basically I can do anything I want. I can go be a teacher's aid for one of my favorite teachers. I can sign out at the office, and go and get breakfast first period, I can sign out 5th period and have a long lunch. I can go to the library and do my homework. I can sit in the senior commons and do homework. I can do whatever I want, as long as I'm not disrupting anyone. It gives the seniors more responsibility. They don't have to report to their teacher, but they can choose to.
My school USED to do a senior class trip too, where the seniors would get a trip to a hotel, or a water park for a few days, BUT thanks to the class of 2008, we no longer do the senior class trip.
Another thing my school does that replaced the senior class trip, is giving the seniors that are in good standing with all their classes, meaning they have passing grades, and have all homework on track, the last week of school off.
Hope this helps, these are just some things my school does.