Senior Class Pranks

I'm in my first year as a high school parent, so I have a lot to learn. This week I learned about senior class pranks when I went by Potomac Falls HS yesterday morning and found that the seniors had staged a takeover of the parking lot. They had a sign directing "underclassmen" back towards the gym. Dozens of them were standing around, lounging on cars, waving the underclassmen cars past. Their cars were scattered chaotically around the parking lot.

I don't know much about this tradition or even about what happened yesterday; I hope people will share more, or tell me if I've heard wrong. Here's a little of what I heard:

• Each year's prank is coordinated with an assistant principal, so it's a surprise but has some prior review by an adult.

• A previous class removed all of the chairs from the lunchroom, with the exception of a few tables that were marked "Reserved for Seniors." The rest of the school had to stand at lunch.
  

• In one year, PFHS seniors built a classroom out of desks. I'm not sure what to make of that one, I get the feeling I'm missing some key info here.
  

My favorite:

• One class put alarm clocks in the ceiling tiles scattered around the school. A few of them were still going off periodically at the start of the next school year because they couldn't be found.