I wouldn't absolutely rule it out. Particularly as we live close to two choir schools, which I have a politics-free blind spot about - I LOVE choir schools. But in general, I think that if you are going to go private, you have to stick it out for the duration, and that is a HELL of a lot of money. dh changed from state to private to state at sensitive ages, and had horrible times throughout.
I would discuss it with them for a very long time, would involve them in all visits, and would also repeatedly present them with the whole lump sum to think about - e.g. 'this is a minimum of £45,000, are you sure?'