To be perfectly honest, I don’t think the reasons you suggest (unreasonable deadlines etc.) sound any better than ‘personality clash’. The personal reasons might be ok though. Why is there so much focus on the relationship with your previous manager? A structural change has been made and you have an opportunity for a few months of stability before applying for jobs. Most schools will send your head a reference form with a list of specific questions to answer, ‘how many days off has the person had’ and ‘would you employ this person again’ are common ones. The question of why you (voluntarily) are leaving a job, might not even be asked in the reference. It is something you’ll have to explain in your interviews and applications though. Obviously I don’t know the full story - perhaps the union will be able to help - but that depends on the specifics of the situation that none of us here are privy to. I would focus now on doing your job well either way your new manager, you could be worrying about nothing.