hi my name is Teferi And i'm wondering if their is a way to hack all school computers at once.
Depends upon what you mean by hack? Do you mean DoS? If so, the answer is yes.
PSTools allows you to execute one command for a file full of IP addresses or computer names. A command could be as follows.
This would execute a shutdown command on each computer inside the file specified (C:\PStools\computers.txt). If there is no luck, your IT Administrator has probably set up a Domain account to control every computer in the school. To crack this, an OPH-Crack Live CD may be used, or OccupyTheWeb's Hack Like a Pro blog on Windows Password Hash Cracking. PSTools has a range of commands, from Stopping/Starting services to Shutting down computers to even establishing a remote Command Line.
Hope you find what you are looking for.-Jarod
as far as i'm concerned, you can't shut them down all at once BUT you can crash the network so nobody can access there files.
check out my post about DDossing here and use a usb to transfer loic to your school computer. run it and attack any network with 100 threads. until you close the program, nobody will be able to browse the web or access there files