I remember in early secondary school there was a weird desktop that would briefly flash during the login process. A friend and I decided to keep logging out and in and furiously click around to see if we could access it, one of the times we did it and that desktop session stayed, there wasn't anything special about it besides a blank windows command prompt, we closed it...

Cut to the school computer systems being down for over a day and noone knowing why, felt pretty scared of being found out over the following week!

Net Send * Hello

Mix that with a c++ loop of While 1 and you have every computer in the school lock up before crashing the network.

Replaced the Windows 95 boot screen with an exact copy where a single black square was changed to red.

Background on a lab to a high resolution naked mole rat picture zoomed in so it kinda looked like a scrotum maybe, but it wasn't: It was just a naked mole rat.

Installed Real VNC server on the machine next to us and connected to it with a small Real VNC viewer window. We moved the mouse over the viewer window from time to time to fuck around with the guy who was using the "target" PC. IIRC we also did the classic desktop screenshot wallpaper prank. In the end they formatted the machine.

Our school used to have a central windows server host and virtual environments for each student seat. They all had only a monitor mouse and keyboard that connected to the server using a username (all started with stu and then the number of the seat) but had no password.

A buddy of mine then went ahead and made a .bat script that somehow simultaneously tried to connect to all student seats, resulting in each of the screens blacking out one by one for a while, then going back to normal.

I ran it for shits and giggles at the end of class, and the teacher saw it, didin't understand what happened initially, got really angry and walked into a few chairs tripping up trying to catch us, and then took us to write a report with the school secretary. I love this teacher, this was one of the funniest moments in school.

We had typing as a class, oriented toward business typing proficiency, words per minute, that kind of thing. This was running on PCs with DOS running WordPerfect 5.1

They were all running some network software (netware) so the teacher could see screens and things. There wasn't a school wide network at the time, but I remember finding out how to send messages that would pop up on the bottom line of the screen of one or all the computers. .

.bat files to open meatspin until explorer crashed Setting tasks to open a video file on login

Nothing crazy or software related, but screwing with people with a wireless mouse with one of those tiny receivers is pretty funny.

In 9th grade (1984), I had a typing class using IBM PC Jrs. I made a quick and very simple breakout game in BASIC one period and distributed to the rest of the class.

I was in a programming class in the 9th grade in which we were taught Visual Basic. I found out that you can run other executable from applications written in Visual Basic using the Shell command and that this bypassed whatever restrictions they had placed on our computers. I could open any Windows XP (I think?) admin utility this way. But more noticeably, I could open the previously disallowed crappy space pinball game. I showed this to some of my friends, and they did the same. A few days later, some of them are suspended for, no shit, "hacking," because they were caught playing pinball. Not me, though. I kinda resented that.

Oh, I also did an infinite loop with the "Beep" command in it and this caused my computer to bluescreen and not come back.

On a school Mac I figured out using some command I could create a new admin account. I used this account to gain access to the school WiFi password and admin account password. I found out what a vpn was and brought my own laptop to us instead of the crappy ASUS Eee PC netbooks. The Vice Principal was not happy. They called my parents for a meeting ( I had a lot of issues with many IEP meetings). My parents were okay with it.

We would also pass around pirated GTA 3, GTA Vice City, Free versions of Minecraft, and Halo CE and run them off of USBs.

Kept removing the web filter proxy from all the browser settings lol the it guy got pissed all the time but didn’t have a way to stop us

The term "Xennial" always resonated with me. We were the ones that were on the cusp of the ending of the Gen X era and the beginning of the the Millenial era. Also 1979 here.

we installed Duke Nukem 3D on all of the computer lab pc's

would put portable games on the public network share, apparently they didn't have logs of people putting stuff there

Modified autoexec.bat (to run a choice with errorlevel excluding to continue all keyboard keys except capital S) with some ASCII art and writings of a virus infection...was the only pc in school at that time...pc got wiped and reinstalled...no one was thinking of exiting the script the stupid way and look around for the causes.

Apparently changed my grades. I really don’t remember this but my Mom reminded me the other day. Luckily this was the 90s and nothing came of it.

Dropped some extensions on the Mac image servers, toyed with Next machines, all kinds of shenanigans.

We would feed the lyrics to explicit rap songs into SimpleText on the Apple machine's and fire up text to speach and then turn off the monitor so it took a while for whatever teacher or authority figure was around to find it.

I recall "Fred" had the best rhythm of all the available voices.

I edited autoexec.bat to put it in to an endless loop :P

We had a small computer room with about 30 computers so I ran a dedicated server for CS 1.5 and told all my grade the ip which they used to connect Counterstrike from a usb. This was back in 2006. We would see people connect from the library and other school computers. Was alot of fun running admin mod.