For a fundraiser that's particularly suitable for high schools, look no further than this one.
You get your students to purchase raffle tickets where the prize is for the winner to spend a school day with their feet up — in practice this could mean using a reclining chair, for example.
The special easy chair needs to be moved between classes or meetings, so make arrangements for this ahead of time. You might also want to sell an “upgraded” raffle ticket that gives the winner the privilege of being pushed around (you'll need a chair on wheels or a dolly to achieve this, of course).
There's no harm in doing the same raffle several times a year or even monthly if you think it's appropriate. Another idea is to install a recliner permanently in one of the classrooms or meeting rooms sell time slots for use of the chair.
You can easily combine this raffle with others as well. Outside of schools (in the workplace for example) you might find that an auction is more appropriate than a raffle and can raise more in the way of funds. Choose whatever format works best for the people you are aiming the event at.