I want to let students use my ipad in the school I work in but I don't want them to be able to access my emails...is there any way of 'protecting' my email....password?

Not that I am aware of. You can put a passcode on the iPad, but thats global for everything. What you may be able to do is to disable (turn off) the mail account in Settings before you let them use it. You can also set restrictions to certain apps under Settings-General-Restrictions.