You could tell her that you've contacted your new employer and arranged a later start for the new job to allow you August in the UK to get organised! I'm surprised that the union are not supporting you on this. I agree that a call to HR is in order. Also check your contract (ask HR for a copy if you no longer have one). If your head's version were correct, she wouldn't need you to be providing her with the dates she's insisting on in your resignation letter. Stick to submitting it by 31st May 2011, specifying leaving your employment on the 31st August 2011. Contract teachers' pay is for 195 days per year and the remuneration for those 195 days is evenly divided over 12 months. You'll have done the 195 days and will be entitled to the full annual pay. Don't be brow-beaten on this! The Head has no authority to have you, or any other, teacher available for work in August. You could be booked on a holiday in the UK or abroad for the whole of August, after all. If she tries to force your hand again, ask whether she will be withdrawing holiday pay from your colleagues doing exam marking, holiday playschemes, bar and restaurant work or car boot sales in the summer holidays! She is definitely mixing your situation up with the pay rules for teachers changing schools within the same or another UK LA.