Philip Hensher: Private schooling is often a worthless expenditure

Except for one or two immensely expensive schools, a good state education is the best option

The movement of educational standards, up or down over time, is a notoriously difficult thing to measure. The tools we have are principally public examinations, which as anyone can see, both in their grading proportions and in their nature, are tools themselves in a constant state of flux. It is all a little bit like trying to measure a jellyfish by using another jellyfish.

If, over time, the state of educational standards is difficult to determine, it's also difficult to measure the various achievements of different parts of the educational system. Some of the best schools, as every parent knows, are outclassed in exam results by schools whose only view of education is cramming pupils to outwit examiners.

The principal point of comparison within the British school system is between the state system and private schools. Here, the exam results show only half the story. There is no doubt that about a dozen private schools, through a ruthless degree of selection before they will take your money and enormous financial resources, produce results by any standards in excess of anything achievable by any state school. On the other hand, there are still many state schools which outclass all but a handful of private schools; and some private schools with good exam results on paper in practice don't supply anywhere near as good an education.

Trying to establish the facts of the case, however, is an obviously difficult task. My casual observation is that an A at A-level these days may signify a brilliant and engaged child; or it may mean someone well-trained, or even a student with significant difficulties with the basics of the subject who has manoeuvred through the requirements. I've taught students with an A in English A-level who couldn't use the possessive apostrophe correctly, and who had great difficulty reading a whole novel by Dickens.

One of the more reliable tests of the state of education today, it seems to me, is Oxbridge entrance. Anyone who has talked to an Oxford or Cambridge don recently, or even in the past 30 years, will be very quickly disabused of the notion that snobbery or prejudice plays any part in their selection. Overwhelmingly, they want interested and engaged minds; if they want knowledge which goes considerably beyond the A-level set books, say, that is largely as a measure of an applicant's intellectual curiosity.

To a considerable extent, they have set aside what they would like to ask for, knowing that to demand foreign languages, say, would be to set a barrier against many state school applicants. In practice, Oxbridge entrance is now a matter of discerning intellectual liveliness and curiosity, and very little about taking students who happen to have acquired a large body of factual knowledge by rote or expenditure.

For those reasons, the detailed breakdown of schools' success at Oxbridge entrance in 2006, acquired through the Freedom of Information Act, is of the greatest interest. What is absolutely clear is that the best public schools are maintaining and increasing their supply of students to Oxford and Cambridge - roughly in order, St Paul's, Eton, Westminster, Haberdashers' Aske's, Winchester, Sevenoaks, and Tonbridge pupils got the most offers from one or the other. These figures are rising, sometimes very sharply - from Oxford, 14 Westminster pupils had offers in 2001, 52 in 2006.

Although the figures relating to state school admissions are more difficult to interpret, and tend to stick around the 53 per cent mark, I think there is a determination in Oxbridge to find talent among state school pupils.

The schools that are losing out, clearly, are the less high-powered private schools. This sort of analysis always calls forth cries of rage and accusations of bias from the parents and teachers of St Custards-like institutions. What underlies these complaints is always this assumption: "We've paid a six-figure sum over the years; we finally managed to extract three As at A-level out of Toby; what, is our money no good any more?"

Alas, no. Looking at these figures, I don't see any real evidence of bias against private education; rather, they look like quite a good guide to where you might hope your children get a really good education, rather than the appearance of one. Nothing has really changed. If your child is extremely bright already, and - a disgraceful further condition - you happen to be in the position of being able to shell out a fortune for their education, then Eton and Westminster are, genuinely, intellectual powerhouses.

If, on the other hand, only one of those conditions is fulfilled - if your kid is bright but you're hard up, or if he's thick and you're rich - you might just as well send them to a good local comprehensive. What this rather interesting and detailed chart shows without much doubt at all is that, failing the luxury of one or two immensely expensive schools, a good state education is clearly the best realistic option. If you send your kids to what might reasonably be termed a "sink" boarding school in the hope that they're going to waltz into a great university, or even be given that good an education, I'm afraid you're utterly wasting your money.