[Rolebama]

We had a very 'hands on' teacher at my Primary School. We made a hot air balloon out of metal coat hangers and tissue paper. Set it off in the playground. A gust caught it and it got stuck on the guttering and set fire to the plastic trim on the roof. The heat from the plastic burning set fire to roof. We had a long weekend while it was repaired, along with water-damage courtesy of the fire brigade. After the dust had settled, it was agreed we could build a rocket. There were all kinds of conditions set. Anyway, on launching, it made a bee-line to the same part of the roof previously burnt. This time we got a fortnight off. We were banned from any further aeronautical experiments.

[Mark07]

If at first you don't succeed... 😂

[Drivingforfun]

I'm trying and failing to think of anything comparable that happened when I was at school

I always assumed schools back in the day were super strict but seems they were pretty laid back!!!

[Santa]

I went to a boarding school and although we did "physics" there was no chemistry teacher. We got access to the cupboard where all kinds of chemicals were stored and tried some experiments.

The best fun was with Potassium which was stored in a big jar full of oil. We found that if you cut off a tiny piece and whacked it with wood, it made a small explosion. It also fizzed a lot when dropped into water. I had some fizzing away in a puddle at the bottom of a sink when someone said a teacher was coming. I swept the potassium into the drain and when it hit the water in the "u" bend it exploded and the dirty water just missed me on its way to the ceiling.

They put a better lock on the store after that.

[Rolebama]

We had some very good teachers at all the schools I attended. I learnt how to make a variety of bombs, and how to distill alcohol as well as a lot of things useful in life. How to wire a 3-pin plug, how to knit, how to sew, how to use a variety of tools, woodworking, metalwork, safe use of power tools, how to set a ladder, ballroom dancing, etiquette etc etc...
This was as well as the usual 2 English, 4 maths, 3 sciences, history and geography.

[NMNeil]

We had the old MiniMax conical fire extinguishers in our school and they could be opened up. Inside was a colourless liquid and a bag of a red powder. No idea what they were but if they were mixed they would instantly turn to a foam and get sprayed from the outlet. the foam was controlled by how much liquid was pumped.
So the colourless liquid was put in the bowl of the toilet and the red powder in the cistern, so when someone had made a 'deposit' in the toilet and flushed the handle about a cubic yard of foam was instantly generated and flew out of the toilet bowl, along with the deposit.
It was funny at the time, but the caning wasn't