There is an assumption that there is a simple choice between state and private.
We live in an educational black hole. Slightly better now than when we started but still very challenging. We saw the writing on the wall early. A mum in playgroup told me that she was so desperate for a place that she had delivered leaflets for favourite in the local elections in the hope that he would help ensure she got a place. Our local secondary was 93% FSM and (at the time) failing.
We thought about it quite carefully. Move to somewhere with better schools, pay in additional mortgage, train fares, and commuting time. (The majority approach - seven out of 10 from my NCT group went before school started, all but us were gone before secondary.) Plan to rent in a different catchment in the run up to secondary. (Second favourite approach - including the person who crows on Fb about her moral high ground in choosing state even though the in-laws offered to pay.) Tutor, get religion, identify weird entry provisions. (Again popular though the grammars are a long commute and tutoring starts early.)
Or just pay.
Which we did. Albeit leaving us watching others enjoy a higher standard of living. Luckily we made it through. We did not have much margin, and VAT might have made it impossible.
Was it worth it. Yes. DS was naturally studious and was a good fit for the nearest private school. DD turned out to be pretty dyslexic and received super support. She was bright so was good at compensating, so might well have bobbed along in the middle of a larger state school.
Us using state would have had impacts. We would have moved, adding to pressure on house prices in the catchments of good schools and ultimately would have squeezed someone out. It would also have reduced the social capital in the area where we live, in that we have always donated time, money and experience to the neighbourhood.
After which paying University fees was straightforward. Upthread I think Tizer suggests that repaying loans if you are on a low salary does not matter as you then only pay small amounts. Our view is the opposite. If you are needing every last penny to pay mortgage, and in our case fees, every last penny matters. It is marginal income, having something spare to spend on non-essentials, that gives you a sense of affluence. If DC want to return to London we don't want them saddled with loan repayments.