Step 1: Work out what your school computers have
Step 2: Download a portable task manager
I've found that process explorer works wonders.
download and put a task manager onto your USB thumb drive and its locked and loaded to stop those teachers at school.
Step 3: Fire the torpedos!
first you will need to find out what the name of the application running on your computer which monitors your computer is. If you found this out earlier you would be smart to do so. for lanschool it should be student.exe, most of the programs will have an exe extension
Next you need to SUSPEND the process, if you kill it, it will most likely just restart itself like lanschool does.
Step 4: Finito
have fun, just dont be stupid about it ok?