i went to high school back in the '80s
One of my classmates was expelled for making napalm, and driving to school with it in the trunk of his car, nothing malicious, he just thought it was cool that he made napalm…
did i mention he drove it to school in his Ford Pinto?..
another classmate was at a weekend pool party where alcohol was involved, he got drunk and ended up chasing the girls around the pool…
…with an idling chainsaw and yelling “SHARK!! SHARK!!”
okay, your turn…
A friend of mine dressed up in a tuxedo, took a toy machine gun, and went into a busy restaurant. He stood at the entrance and slowly looked around the room, which got deathly quiet. Then he turned to another guy and said, “He’s not here,” then walked out the room.
I imagine the diners had a lot to talk about after that.
When I was younger, probably in junior high, me and my friend got alot of enjoyment out of mixing various household products together to see what combination would be the most flamable. Each day we’d ransack our parents kitchens, bathrooms and garages for whatever new and exciting cleaning, automotive and haircare product we could find and fill a pop bottle with a unmeasured concoction of these liquids.
Ususally ants were the guinea pigs in their own miniature Vietnam.
There were a few stupid events involving drag racing on city streets in the middle of the night, but nothing all that amusing. Unless you consider the fact that I got pulled over (totalling 4 tickets in 2 weeks) driving a 4-cylinder Mustang while racing a Toyota Previa van funny.
Oh, Lord, don’t even get me started. Our place was a freaking nuthouse.
Me and my friends kidnapped the Calculus teacher’s mannequin (yes, he had one) and held it for ransom the rest of the year. On our graduation day we put the mannequin on center stage with two strategically placed coconuts and a grass skirt (the mannequin was male). It was a lot of fun, wish I could do it again.
We changed the sign in front of the school so it said … something else. The school was on a major road that ran through town so it took some work to do without getting caught.
We took the yearbook teacher’s Honda Civic (Civics were lighter and smaller back then), moved it to another spot in the parking lot and turned it upside down on its roof. He wasn’t as mad about that as I thought he might be.
My biology professor made me sit in a kind of storge area between the two classrooms because I was being disruptive - alternating between cracking jokes and answering difficult questions no one knew the answer to (“YAWN I’m just going to toss out a guess but is it…Deoxyribonucleic Acid?” )
Anyhow after about 15 minutes, I took a skeleton arm I found and started reaching through the door with it, asking to be let out…turns out that was also “disruptive”.
Oh yeah and there was this time the cops chased me in my Olds Cutless Sierra down some railroad tracks and I escaped by driving through a metal gate…but that’s a different story.
In junior high science class we once had a sort of open lab period. My friend R decided the sulfuric acid wasn’t concentrated enough straight out of the reagent bottle. So he poured some in the old erlenmeyer and proceeded to boil off the excess water. Only one problem. The H2SO4 went into the air with the H20. I don’t know what mustard gas is like, but we had to evacuate the school.
I don’t know if they still have open lab periods at that school. R went on to the Naval Academy and had a successful career as a F-14 pilot. Last I heard, he flies for Delta since retiring from the Navy.
We did go through a period of breaking into just about every municipal water tower immaginable because of the nice views they afforded our beer drinking, but mostly just a lot of testosterone fueled insanity with muscle cars and gunpowder. We did though generally try to only pose a lethal danger to ourselves.
You didn’t happen to go to Wet Sex High School, did you? Because that’s what the sign read when we changed it. 
A friend of mine and I learned to make smoke bombs from Abbie Hoffman (not personally, but through Steal This Book). Ahh, the carefree days when a young man could buy saltpeter at the corner pharmacy. Anyway, I just used to set the smoke bombs off in the sewer and such. My friend – two years behind me and after I had graduated – started setting them off at school. He had a bounty on his head for a while, but never got caught.
We used to save up bits of the chemicals we used in our weekly Chemistry class lab, and after a few weeks when we had a good variety, put them all in the crucible (or beaker, or whatever we had), give 'em a good stir, and see what came out. Amazingly enough, we did not burn down the school.
Ah, the heady days of hood-riding. Belly down on your friend’s car’s hood, grab hold of the windshield wipers (or whatever), tuck your feet into the headlight-wells (or whatever) and then – WHEEEE! Your friend drives like a maniac, trying to fling you off, ignoring your pleas to slow down, because just before he took off you shouted (like an eejit), “Whatever I say to the contary, show no mercy!”
If your friend was a true friend, he’d slow down a bit (but not by much) when both of your legs had lost their purchase. Stopping, of course, involved slamming on the brakes and the unstoppable (except by pavement) force of inertia and momentum.
Remind me again as to how we didn’t break any bones?
Overall, I had a pretty sane (read: boring) high school experience (except for the German exchange, but that’s several different stories). Fourth of July my senior year, though, my boyfriend’s friends asked me to go with them to buy fireworks. My BF and his friends were juniors and 17, I was 18 and could legally buy fireworks (in Illinois, anyway). So we drove from Milwaukee to the fireworks barn that was just inside the Illinois border, picked up some Roman candles and a shitload of bottle rockets and headed back. Most of the rest of the evening was spent sticking bottle rockets into hot dogs and pieces of chocolate cake to see if they’d blow up. After dark, we drove to my dad’s house. He’s a very sound sleeper, and the backyard was low-lying and soggy; the perfect place to set off the Roman candles. Afterwards, we still had tons of bottle rockets left. We lived in a very quiet, conservative, upper-middle class suburb, and we knew that if we just started setting them off, the cops would be called in a second. How could we keep the cops from finding us? The answer was obvious: become a moving target. We drove around in my parents’ car with two empty soda cans, a lighter and the bottle rockets. Stick a bottle rocket in a soda can, light it, and hold it out the window. HAH! TRY AND CATCH US NOW, COPPERS!! 
I’m 43 years old and I still think stuff like this is funny :D. Like the kids who took the C off Chardon High.
Forgot to mention that me and my friends were the brains behind the underground newspaper, which was published about four times a year. We had bounties on our heads too, for the rotten things we said about our fellow students, and our rotten poetry Good times.
Ahh, the misspent days of youth.
A favorite activity of ours was to drive up and down the interstate late at night shooting bottle rockets at each others cars. And by obttle rockets, I mean hand rockets, because we didn’t use bottles. We jsts held them on our hands then let go when they lit.
Had a friend of mine successfully make nitroglycerine. Then he had to figure out how to successfully dispose of it.
A lab partner in high school decided to see what would happen if he started mixing chemicals. At some point the ceramic crucible he was mixing in turned red from the heat. Naturally he dumped it down the sink. I can still hear the sizzling.
My biggest “hey, let’s see what happens if we do this” moment came in college. My roommate and I had just moved into an apartment that hadn’t been cleaned well prior to our arrival. Since the toilet was running, I first turned off the water to it, then mixed all the household cleaning supplies we had, including the ammonia and bleach mixes. Then we closed the door and went out to get a bite to eat. I still think I suffered lung damage when I opened the door.
Wow, my brother! I also did an underground newspaper, being very sarcastic and mean to classmates and teachers. Then again, I did it in M.B.A. school. I don’t think they ever put a bounty on us, though. And we never got caught.
The only thing I can think of from my high school days was pretty low-caliber compared to most of the other stories here. One time some friends and I ordered a pizza to go and then proceeded to take it into a competing pizza joint to eat it there. We did this to protest the crappy service we got from them before. After about 15 minutes the manager kicked us out.