Hi Jo

It would be consultation, if you can't reach a compromise; unfortunately you'd need to make the posts redundant.

I would be cautious around framing it as a reduction in their holiday entitlement. This will actually remain the same. You are expecting them to attend work when they wouldn’t normally. I agree with Ella’s response in that it’s a potential redundancy situation. Are they actually teachers working in this role or have they just been employed in a teachers contract?

I am not sure it is possible given the STPCD

It's certainly possible. Almost anything is possible. The question is only ever how much pain are you prepared to endure to achieve it and how much money are you prepared to throw at the problem?

As Ella says, it would require consultation with the affected staff, in which you explain your reasoning and how you're prepared to compensate them for agreeing to the change, and in which they tell you what they're prepared to accept in return for the change, and you decide between you whether you're prepared to give X for Y.

Although, theoretically, a fire-and-rehire scenario is a possibility (assets.publishing.service.gov.uk/.../draft-statutory-code-of-practice-on-dismissal-and-re-engagement.pdf) if you're prepared to be generous in your offer, I would expect to find the staff eventually amenable to the change. If, on the other hand, the SLT thinks that they're going to just be able to change the Ts&Cs without it costing them anything to do so... well, they may require some gentle re-education.