I think you do have to be pretty comfortable to fund school fees. Once all other overheads are taken care of: mortgage, utilities, food, modest car, modest holiday, daily expenses, notwithstanding bursaries or scholarships which cannot be banked on, the cost, here in London is a whisper over 30,000 per annum after tax. So, providing one income can meet all the other expenses the other, if sufficient, can meet the school fees but that is providing there are no redundancies, illnesses along the way. For many families there would need to be a huge number of sacrifices over a many many years to meet the fees for two children.
On the other hand there were a number of occasions at my dc's state cofe when I had to bite my tongue when mothers said "you're so lucky, you have choices". The same mothers in the early days were the ones who said "I wouldn't put up with my DH working those hours and every weekend - I'd put my foot down" and "oh, you're so lucky you got a part-time job". Yes, with a five year plan and on a very low back to the bottom wage to get the professional quals I didn't have in my first career.
As I've said earlier on this thread, we are comfortable, not in my opinion rich but everything is relative and we're certainly rich by the standards of the 50 per week on groceries MNetters but a lot of hard work has gone in on the way. The DH is just reaping the benefits of that work having built up a significant reputation over 20 years. Our house is valuable and well maintained, reasonably co-ordinated but by no means cutting edge or ritzy. My car is 10 years old, the garden is a generous 80 foot (which is large(ish) for this part of London, the DH wears reasonable suits a shirts for work, I don't do designer but have a few good pieces. The DC wore George and M&S when they were younger but seem to moved onto Jack Wills with a combi of River Island and Top Shop. I have my hair done every 6 weeks but have never had my nails done or seen a beautician, but do outsource the cleaning and laundry (our cleaner, a lovely Polish girl, lives in our spare room and works gratis). We have one holiday in England, one in France and the boys go ski-ing at Feb 1/2 term. I certainly wouldn't have a swimming pool, the maintenance is hellish and the associated expenses - not least the cost of entertaining too many visitors - are ridiculous. I might buy one Radley handbag (or equiv) a year and have no desire to own a pair of Jimmy Choos. Sitting here in a six year old pair of splitting Joseph Siebel sandals.
What is for sure is that we didn't get here by making daft choices, I didn't get pg by mistake before I got married or live with anyone or get involved with people who might have been a bit dodgy, or go clubbing on work nights and neither did DH.