We installed quite a few games on the backend server.

• worms
• Unreal tournament
• doom
• Quake

And a few others. They were there for years, if they were deleted we had backups in multiple spots had them there for at least 4 years.

A bunch of people at my school would flick the power input switch on the back of the PCs to 110v (240v native in my country) while they were off and wait for an unsuspecting person to come by and boot it up. It'd obviously go bang and start smoking and they'd freak out not knowing what they did to cause the PC to blow up.

Shit move, but having witnessed the shear horror of someone who thought they caused it to blow up was kinda funny.

I had GLTron and Pocket Tanks installed on a flash drive, so my friends and I would just play games whenever we had free time.
I also found a couple fun network based utilities in Windows, and all the computers in the district were on the same network. I was messing with NetSpend one day and managed to accidentally send a message to every computer in the school, which then all promptly crashed for some reason.
I also had fun messing with the netchat application. My mom worked at another school in the district, and one time I arranged for her to open netchat at a specific time while I was in computer lab, so I could connect to her computer from a lab computer and we could chat back and forth.

We installed Doom on a couple computers, this was in '97. Our computer teacher had absolutely no idea how we did it. Private schools were fun for running circles around the teachers.

I used to goto cartoon websites and play unallowed computer games, nothing inappropriate, just spongbob stuff, which got me permanently banned from watching spongbob at home.

The school would keep using Internet Explore 6, I'd update it to iE 8. They didn't like that.

I'd also would install some toolbars, there was this one yahoo one, that added tabbed browsing to iE6. :)

Updating to iE8 on only one older computer caused problems, but the newer machines worked fine with iE8. ;)

I would install Firefox, Opera, Google Chrome and Apple's Safari for Windows web browsers. I enjoyed testing and find the best browsers back then.... Staff weren't to happy though.

I'd change desktop wallpaper to windows XP's Bliss, instead of the schools preset solid colour background.

As i got older, I learned how to write batch and vbs scripts to automate different things, so i wrote a tool to automatically login to some of my required school accounts, without me needing to manually type in my login credentials each time. Staff either didn't know or didn't mind this.

We installed Doom (1 or 2, I don’t remember) in an invisible folder and played via the 10Base-2 network. Those were the 90ies…

installing linux as dual boot, well it fixed the windows 7 that couldn't update lol

We never had school computers :(

Write a script to create an neverending amount of files. Piratinh games. Trick teachers into giving us their passwords. I could go on...

Install NixOS on them 😈

Netbus 1.70 baby

Installed ventoy to a 32gb flash drive, turned off secure boot and then load into any distro on the drive

Also had a persistent windows installation on another drive

Set up fork bombs to trigger at random intervals.