Just to elaborate (because I didn't think that we could afford it either )our finances work out a bit like this:
Monthly drawings:
£2500 to joint account (all house bills)
£975 to school fee account (includes lunch)
£540 to my account (Clothes, shoes, holidays)
£540 to dh account (mysterious black hole)
This equals £4500pm from the business. We pay tax every January and July and we supplement our income with extra projects along the way.
Once you are self employed I think it is easier to find other projects to generate some cash because that is the way your mind starts to work. When we were employed we just used to accept our salary, now we tend to be a bit opportunist.
I completely agree about the 'middle income' trap. We sold our posh house in a nice area to live in a much smaller gaff (but equally nice to my mind) in a less nice area to make the jump to business ownership. It wouldn't be for everyone.
Our fees jump this September with the eldest starting Seniors and his sibling just a few years behind. We have been planning for the last 18months how to factor in the increase and have taken on a bit more work in advance. I really believe that you have to plan, plan, plan.
Also, we have no debt or finance apart from mortgage. Our cars are paid for and basic and I'm never going to win any fashion or grooming prizes. My kids wear secondhand uniform and none of us gives a sh1t about it.
Anyway, that was a ramble. We've been doing it for years and we manage fine but it is a huge commitment. The teachers get a 45% discount at our school but their children cannot be awarded any scholarships.