This is just wrong; and clearly your strong point as a governor (I’m also a school governor and a trustee of two additional educational charities in the non-school sector) was not the finance side.
Much of the increases in staffing costs has been not in “inflation busting pay increases”, but in pensions costs, NI and other overheads, including general inflationary costs that have risen dramatically in the last few years. You are confusing cost increases with how you can make cuts. The costs of running any business have increased because of huge leaps in the cost of energy, food, transport, maintenance of buildings, etc. All businesses have been facing increased costs. But contrary to what you are assuming, private schools cannot actually cut those costs easily. (The average school accounts for an independent school look pretty much the same as a state academy. Could your state school easily make 20% cuts in its budget? If not, why do you think the average independent school can? Their budgets don’t look much different.)
If there’s been a lot of inflation in energy, general running costs, etc., you can’t just cut that. You can’t just make those 20% cost savings on inelastic costs. The only things you have that you can cut is staff. And contrary to your perceptions, most private schools are not actually full of a huge “pyramid” of staff and they are not top-heavy with overpaid people. The vast majority of private schools are not Eton. They really do not have lots of staff being overpaid. As you point out, the staff are not actually paid huge inflation busting figures. So, follow that through, and you realise that if you start cutting staff, it’s the teachers and admin staff and ordinary employees who suffer. Is the Head going to be cutting him or herself? They’re probably paid on average not that much more than an Academy head. Would taking a pay cut of a few thousand suddenly make up for 20% of the school’s operating budget? (Don’t be daft.)
Most private schools have already been subject to huge increases in pension costs which have caused some to have to come out of previously highly valued pension schemes (eg. GST schools). It’s just simply idiocy (and financial illiteracy) to suggest that private schools can easily save 20% in costs without making staff redundant. And what’s the bloody point of that? Stick it to the rich parents but at the expense of making more music teachers, admin staff, maintenance staff and dinner ladies redundant? Is that the Labour policy you want to see? Doesn’t seem that redistributive to me.