So annoying that any question about private education turns into a thread about private vs state. It’s a perfectly valid topic, and somewhat ironically I agree that private schools shouldn’t exist, but while they do I will use them if I can - but the debate doesn’t address the matter in hand.
Like you, OP, we are a two working parent household and send our DD to private school. Yes we have a good income, but we made a choice to prioritise our DD’s education so our income is stretched and fee rises will be very difficult. As someone who is a second generation immigrant, my parents sacrificed so much to do the same for me (even seeing their family back home less) because to them (and me) there is nothing more important than education, at the right school for the child. For them, it was also a way to balance out the racism and sexism I would likely face in the job market and workplace. And it undeniably has helped with that. It remains a factor in our choice for our mixed race child. We know we are exceptionally lucky we can afford this choice.
If fees go up a lot more, I’m not sure how we will manage but we put aside any leftover money each month into an account to address likely increases in the future. Rises are inevitable. I don’t know that we’d manage if VAT becomes payable. It won’t stop me voting out the Tories though, whose policies across the board ONLY assist the ultra rich. I think many at the school would struggle if VAT becomes payable - I can only think of 2 really super rich families in DD’s class. Everyone else has two working parents and there is a lot of chat about the fear of losing an income.
Our school fees have gone up this year. Though they have not gone up by as high a percentage as yours, the starting point was much higher. We are in London, so that’s inevitable but they really are MUCH higher than yours and so I saw your post and thought that was pretty good! Schools have rising costs like electricity and wages to meet CoL issues for the staff (not just teachers but ALL support staff including the cooks and cleaners etc) so I think increases are fair. It is important to recognise that schools are not profit making, so when there are rises in costs, they have to be met by fees.
So I don’t think the position is unfair, albeit that it is tricky. Good luck OP.