OrangeBlossom, that is truly an awful to wake up to. Hope you can try to out it in the back of your mind until you really need to deal with it. That sort of thing stresses me out mightily.
It's worth knowing your employment law and union position, not because it's worth them getting involved (in fact, it often isn't in terms of stress and cost - and if the school 'manages you out' cleverly, it's really tricky to do anything about it anyway). However, it will give you confidence to ask the right questions, which can worry the school and make them treat you with a bit more care.
Devote a bit if time to thinking of a plan B if they do manage you out. E.g. If you don't want to return after the holidays, you might consider not burning too many bridges in order to get a decent reference...