here are some sites i found to make a basic virus
http://www.instructables.com/id/Computer-Prank/
http://www.instructables.com/id/Code-an-easy--virus/
http://www.instructables.com/id/EW7A6THQLEES1760XQ/
and one for your school
http://www.instructables.com/id/Shutdown-Your-School!/
havent tried them but planing to at my moms school lol good luck hope it dosent get shut down

first one isnt a virus in the least... the second one isnt either, and it's coded poorly... the third is probably the most script-kiddy-esque thing to hit the market since Sub7... the third is the least shitty of all of them, but still; is not a virus. stop being a script kiddy and while you're at it learn how to code something other than Batch.