A: I assume from your question that your new job is still in a school. There are fixed notice periods for teachers meaning that they leave their jobs at Christmas, Easter or the summer. With six-term years and some schools starting the academic year in August, give and take is often required, but authorities, if not individual heads, understand this problem.
Unless you are a head, the notice period is normally two months for resignations that take effect at Christmas or in the spring. For the summer, it is the last day of May, with pay up to the end of August.
As to what you should write in your resignation letter, there are different schools of thought. I would be tempted to keep any letter short and to the point. In this case, just saying you are resigning because you have found another job. Avoid the temptation to make comments about the school that either might rebound upon you or make it unlikely that you could go back for a reference: you don't know how the new job will work out long-term.
One word of warning, especially if your job is at quite a senior level: do take advice about your pension. Non-teaching staff do not normally have access to the Teachers' Pension Scheme. They usually belong to local authority pension schemes that are funded locally and by investments. This may also be something to consider if your new non-teaching post is outside of a school. Teachers going overseas also need to take this into account as part of their financial planning
John Howson is a recruitment analyst and visiting professor of education at Oxford Brookes University. To ask him a question, email him at email@example.com