What is the correct process for applying to schools?

[Watercress99]

Silly question I know. But, are you allowed to attend an interview and then if you’re offered a job and you think hey this isn’t for me right now. Do you have the right to say no? Or is the issue when you say yes to a school and then pull out last minute? I’m just not sure which one it is where employers view it really poorly?

They'll ask in the interview if you're a firm candidate. If you're not, you say no.
You can withdraw at any point up to then. Once you accept an offer though, you'd be unwise to withdraw.

Instead of no could you say I do have an upcoming interview at x?

You can but some HTs will take that as a no.

If you have two interviews and would prefer the second one, you might be better contacting the second school and asking if they’d be willing to interview you sooner.

@AttaGirrrrl I haven’t heard back yet as I just sent the app off today. It’s so stressful at the min with other deadlines too

You're allowed to withdraw before the day, or at any point during the day. I've also known people reflect on their way home from interviews and withdraw prior to the panel making a decision (situation for roles where there's been several days of interviews).

What's not OK is to accept a job at one school, then interview at another.

If you were to say "I have interviews at X on Y", some heads would see this as not really wanting to work for their school and retract their offer before you can decline, if you were successful elsewhere.

A job in the hand is worth 2 in the bush. The market is tight and i think you would be foolish to withdraw from any applications. Get a job for September and then there is plenty of time to make another move in a year or 2. Unlike virtually every other job, you will be expected to accept or decline on the phone/in face at the time of offer, and you cannot change your mind.

As above. It's one of the worst things about teaching!