Mostly, however, people pay school fees because that way, they believe, they are buying a better education. And fees being what they are, they want to see results.
Traditionally, of course, fee- paying schools have always achieved the highest examination grades, and national newspaper league tables, studiously ignoring added value, do much to strengthen this perception. The great independent schools, all highly selective and drawing from national or city-wide populations, are in the premier league. For most fee-paying parents, however, these schools are quite inaccessible - so they turn, instead, to the local tables. And in the local tables, which come nearer to ranking like with like, they get a different picture.
For the last six years have seen a countrywide improvement in state school performance. Over half of all entries at GCSE are now graded A to C and it is not at all unusual for state comprehensive schools to see half their pupils gaining five or more such grades: the magic key that opens up to them the whole highly competitive field of 16-19 education. Already, the effects are showing through at age 18, with four in 10 of the age group now entering for A-levels and getting an 80 per cent pass rate.
At last, state schools are beginning to unlock the potential of the whole range of their students - and parents in the system seem to know it. Both the Mori pollsters and the new Ofsted parent surveys now show a consistently high level of parental satisfaction.
Private schools still have one considerable advantage. As last year's National Education Commission showed, they spend a great deal more than state schools do. In 1990-91 they spent on average pounds 3,206 for every secondary pupil against the state school figure of pounds 1,926 - and the gap is growing wider. Much of the difference is due to smaller class sizes in the private sector.
But all the evidence shows that smaller class sizes do not, of themselves, translate into better learning and better results. What matters most is the quality of the teaching - and in this respect the ordinary fee-paying school may be at a disadvantage. Private schools cannot offer their teachers the same width of experience that state schools do, and they are unlikely to set the same professional challenge to them. When I moved from independent school teaching to the state system, it was the first time I had encountered children who apparently did not want to learn. As a teacher, that really stretched me - and I became a better teacher for it.
When you are faced with the whole range of learning need, you have to constantly sharpen your skills. Good teachers in comprehensive schools are very good indeed - and have more opportunities for promotion.
So the question of whether private education pays is an interesting one; an important one, too - and not just for the individual parents who have to look at their bank accounts and find an answer to it.
Private education in this country is heavily subsidised by the state. Assisted and aided places, LEA-funded places, boarding allowances and tax concessions add up to a very substantial sum. If private education is by definition better, that is right and proper. If it is not, we may be selling a lot of parents short. And a lot of children, too.
The author is headteacher of King Edward VI School, Morpeth.