What's the going rate for an A-level A grade?

With my 18-year-old son's A-level results due on Thursday, the financial incentives have been in place for some time. Basically, we are talking £50 for an A grade, an extra £20 for an A*, plus a further £40 should he secure top marks in all three subjects, making a potential grand total of £250. A startlingly munificent gesture, I assured myself (it was £10 for an A in my day), only to discover from last week's newspapers that the average middle-class cheerleader will happily part company with upwards of £750 this week and that, by the standards of his peer group, Benjy's fond parent is one of the biggest cheapskates on the block.

Even worse than the thought of miserliness was the implication that promised rewards of this kind were merely just another form of middle-class self-advertisement, a kind of status-hungry preening, designed to reinforce the bourgeoisie's sense of its entitlement that we hear so much about these days. Sensible parents, one inferred, were perfectly entitled to exult in their children's achievements but should not indulge in the conspicuous triumphalism of large sums of money, electronic gadgetry, and – if some of the rumours from the playground are true – motorised transport.

By chance, these reports of the pots of gold waiting to be dug up at the end of the sixth-form rainbow coincided with a survey by London University's Institute of Education into the effect of free schools on disadvantaged communities. This suggested that such institutions "cherry-pick" the bright and wealthy. A particular sentence in the report stuck out: "It appears that, so far, the places in reception are being filled by children who are somewhat less disadvantaged and more advanced in their development than the average." Those middle-class mums and dads again, you see, jumping in to get preferential treatment for their privileged tinies! What can be done about them?

The regular public complaints about middle-class "pushiness" – most of them, it must be said, pronounced by middle-class observers in middle-class newspapers – nearly always produce a feeling of bafflement in this particular member of the upwardly mobile bourgeoisie. Governments (of left and right) set up a series of social arrangements and educational institutions expressly calculated to spur the ambitions of the middle classes, and then wonder why it is that they jump to take advantage of them. Naturally, the interests of that highly desirable abstract social equality will not be served by middle-class dominance of the free schools, but, really, what did the Institute of Education expect?

Such hand-wringing over the relatively well-off's pilfering of opportunities that were supposedly meant for other people is even odder when seen in the context of recent British history, for the middle classes have been launched on their long march to prosperity and influence for centuries. Although the roots of bourgeois self-aggrandisement can be traced back to the pre-Georgian age, its key moment was the early years of the Victorian era. Blessed with a monarch whose values it shared, the middle class not only came by political power but rapidly acquired the social and financial heft capable of buttressing it. The significant thing about this demographic explosion was its equally rapid transfer into mainstream culture. The novel, for example, is almost by definition a bourgeois medium, with cinema not far behind, and the middle-class stranglehold on art lasted well into the second half of the 20th century.

A Marxist would probably write these developments off as a capitalist plot, but the Marxist who paused to examine some of the individual histories of middle-class existence in the past century or so might possibly end up by acknowledging that human aspiration has a life beyond politics and that not all the people who want to "get on" do so out of a wish to tread their neighbour's faces in the dirt. For large numbers of those who determined to clamber up the social ladder in the early part of the 20th century the process was a struggle, bringing a terrific sense of exhilaration but leaving scars that, in some cases, never healed. Some of the most affecting passages in Richard Hoggart's classic The Uses of Literacy (1957) dwell on the luminous figure of "the scholarship boy", the young man breaking through the class barriers that hold him back, delighting in the freedom that will now be his, but fearful of leaving the security of the world that created him.

My father (born 1921) was a classic example of this kind of social mobility: born in rented "rooms", transferred, aged five, to a council house, encouraged by his proudly possessive mother to sit "the exam", borne aloft on a tide of scholarships, white-collar jobs and private accommodation and, to be perfectly honest, made neurotic by the difficulties of the transit. Again, a Marxist would probably have urged him to have been true to his class – not realising, of course, that the British working class is about as homogeneous as a jar of marbles. But Dad didn't want to stay becalmed on his Norwich council estate, and the snubs he picked up while pursuing his exit strategy were a price worth paying.

Needless to say, I admired him profoundly for all this – how could I not? – while remaining uneasily aware that there were other people who lacked his advantages, his drive and his tenacity. And what is to be done about them, while the modern middle class goes about infiltrating its children into decent comprehensives, paying for the extra tuition that will enable them to shine in public examinations, twisting every situation in which it finds itself to its own advantage and demonstrating the kind of ineffable complacency displayed in everything from the public utterances of Jeremy Clarkson to the average Daily Mail leader?

But there is something else to be said for the middle classes – or one of their particular specialised redoubts – over the past 70 or 80 years, and that is their intermittent radicalism. As political historians never tire of pointing out, the Labour Party, until comparatively recently, was a kind of pantomime horse pulled in separate directions by the mass of organised labour who secured its finances and the middle-class intellectuals who attempted to formulate its policies. Nearly all the enlightened social legislation of the past half century, from the ending of the death penalty to the decriminalisation of homosexuality came from the latter camp.

So, yes, we are dreadful, us upwardly mobile arrivistes. We are – or rather, our fathers were – traitors to our class. We scheme to advance our children's interests and lavish money on them when they triumph. We want them to excel – as if any parent actively wanted his or her offspring to do badly – and we expect the country to be run in our interests. Yet, when it comes down to it, we – or some of us – are remarkably public spirited; and if quite a lot of our dogged, self-satisfied national philistinism is middle class in origin, then so is some of our tolerance and respect for individual quiddity and belief. And so I shall be signing the cheque on Thursday morning with a glad and confident hand.