Depends on what network the school has. Could be RM, or could be using the Active Directory. Both have pros and cons.
Unlike businesses schools are not willing to throw vast amounts of money towards IT, so you have average machines running on below average Servers. this is what slows the network down, along with cheap switches etc.
Staff prefer to see what the money is being spent on, i.e. a new class full of PCs, rather than updating an old server.
Internet will probably be governed by the LEA, who will have filters left right and center.
Most common jobs will be adding users, resetting passwords.
simple things like "My printer doesnt work, when i click print, it prints to the one in the corner, not the one on my desk" so showing staff how to change printers in the drop down box etc.
Will you be in charge or is someone above you?
You may also have a online registration system, such as SIMS. this is used instead of pens and paper to mark the register.
You may have to look after the school website too.
Do you know how big the school is? how many staff? pupils?
Didnt you ask these questions at interview?
And make sure the backups work correctly too, that is important.