A new prospective employer (usually the head of the school you are applying to) expects to be able to talk to your current head from the moment you apply.
This in turn means that you have to tell your current employer the moment you start looking for jobs elsewhere.
Any other references are done before interview, not during an offer. Your referees will be writing a lot, on your behalf, O(n) — jobs applied for — and not O(1) — job offers you want to accept.
It is considered obstructive behaviour to not be open about your current salary. You are immediately viewed as “difficult”: just like candidates who apply without telling their current school, so too with candidates cagey about money.
Taking time off during term is not allowed. Taking time off to interview will be deducted from your pay unless you get prior approval, and you have to declare that you are interviewing.
Resumes / CVs are not allowed as part of the application. No one will read them.
Some other gems, when negotiating salary: “b-but no one goes into teaching for the money!”, “sorry we don’t aim to compete with the commercial sector”, and “we don’t define the hours you’ll need to work, only that you do what is deemed necessary and appropriate” only to later be told that it’s not the done thing old chap to work any less than 50 hours a week.