Well every school network is different and it depends what you mean by "hacking".
if you mean like accessing admin accounts e.t.c theres like proper ways of hacking but what I did to get into admin was I saw my teacher logging on so I saw his user name...and on our system you can send password reminders so I guessed (after many attempts) the recovery question for his email and emailed a reminder...logged on as him....unblocked every website and deleted all the other admin accounts. this took me like 3 days and most techys wouldnt call this hacking this is just like guess work than hacking.
(The Ginger Scot!)
~Laura was here~