Try this page. WARNING: Some curse words ahead.

Because, you know, Ultra, everyone has industrial-strength equipment on hand for welding people's doors shut (while they're inside, no less) or rig toilets to explode while people are sitting on them .

As for the original topic of needing a prank;
Do what the grads did last year; get 2 (or however many) pigs (or piglets) and paint numbers on their sides in sequence.
However, skip one number in the sequence.

E.X. Get 4 pigs and paint "1, 2, 4, 5" on the pigs.

The staff drove themselves crazy looking for number 3.

Not at liberty to really SAY what I did. I WILL say that it involved a couch, main street, a six story building, gas, and 4 matches.

~Rico

Because our senior class was a good class, we painted the large M (For Manual High School) baby blue and the lightning bolt (Even though we are the Manual Thunderbolts) red for our senior...prank. Of course I didn't paint, I just supervised...

Anybody who participates in Senior Prank Day at our school gets an immediate referral. In fact, during the last few days of school, nobody's allowed in our Atrium on the second or third floor, so no senior (or poser junior who wants to get their own laughs) can drop anything as has happened in the early years of our school. :3

However, my dad told me of an amusing story of when he was in college. He and another guy were good friends with a member of the faculty. My dad had created a replica of the Master Key that can open any door on campus. One day, while the faculty member was out of town, my dad and the other person decided it would be a good idea to take apart the stalls in the nearest bathroom and recreate it in the faculty member's room.

So if you can imagine leaving for a weekend and coming back to your dorm (or whatever it is) to find a public bathroom pretty much reconstructed in the middle of it, you can imagine how confused the guy was. And to this day, my dad and his friend weren't caught, and my dad still has that key.

~Shadowed Spirit Sage

is this some american version of april fools day..? (no wait, you have that day too, right?)

the only 'pranks' kids did when i was at school would be to set fire to the toilets, drop stink bombs or hide my school bag in various places.

Basically on some specific day of the school year (it will vary by school), the kids that will be graduating at the end of the school year attempt to pull off some elaborate prank. While I can't say with 100% certainty that no one would pick April Fools Day, I doubt that anyone would choose that day for their "Senior Prank."

Well, the ony thing to compare with my school is that on the last day, we did pull some pranks.

Filling the head of sixth-form's office to waste height with ballons (and superglueing his phone down =D) was the main one, though somebody was clingfilmed to a car, and I led a pirate invasion of a PE lesson. Things got a little silly when some people then started slowly driving their cars round the school field after year 7s at lunch....

Some previous ones have involved holding dustbins to ransom, and hanging the novelty hippo dustbin from the school chimney. An unused suggestion, was moving the entire sixth form common room out onto the field in it's exact layout =D

On our last day people brought in screwdrivers and removed screws from nything that had them, chairs, tables door handles etc. Some guy even brought in their electric screwdriver so the managed to cause the most havoc.

Also someone went around switching the computers 110/220 v power supply switches.

*boom*

The most evil thing was the placing of fish in the ceiling or wall panels.

I have actually forgot the last few Senior pranks on the last day of school.....

I believe it was last year that big ol-fireworks were set to blow ontop of each rooftop, since we have one of those large, open outdoor campuses with a lot of buildings, and after the first final they all exploded a few minutes as we were on the 15 minute break.

...I don't know why I can't recall the others. >_>

~T2K