I don't work, but we don't private school (and DH doesn't earn 100K).
I have friends who do send their DCs to private school on 60-70k, but with a much smaller mortgage and with help from GPs or scholarships. Others income I can only guess, but I suspect one parents money goes purely on fees.
The thing is that people come at this income level from both sides. To me it's a nice amount of money, I enjoy being able to have a holiday most years and not count every penny spent.
Neither DH or I went to private school (his sister did, but a sweet little girls school, did state sixform to get good science grades), so we don't see scrimping, saving, me working and relying 100% on paid childcare with all it's stresses is worth it.
Other friends come at it the other way, from business men, professional and high up public serve to Fathers and possibly family money, they went to private school. Their friends DCs go to private schools. Their DCs will go to private school!
Sometimes I'm not sure they've done the sums with modern school fees, housing costs, interest rates on savings, energy bills, petrol, extra curricular stuff, etc etc all of which have gone up, especially if you own a nice big house in the country side.