It is time to come clean. I have a secret. In many respects I am a fairly typical inhabitant of this land. I love the country and its culture and happen to believe the Scottish parliament does a good job most of the time. I'd relocate Trident to the Home Counties and repatriate North Sea oil if I could. I worry about poverty. But I have broken the great taboo of supposedly progressive Scots. I have used private schools. I neglected my egalitarian duty to use my kids to raise standards in the state sector. I endorse an option that has few public defenders in the political and educational establishments.

Yet I am not in such a beleaguered minority as might be supposed. Fees may have risen by 40% in the past five years, but figures released last week showed the number of pupils in independent schools is rising in Scotland. Private schools may be regularly denounced as a social evil and must defend their charitable status - but a growing number of families ignore the negative propaganda and embrace the blazer.

I suspect many are just like me, professionals from working-class backgrounds. We were the first in our families to enter university, and we know better than most the life-transforming power of a decent education. We are also likely to be of the generation that experienced the early years of the comprehensive experiment. That factory-style education is not what we want for our children.

I should say here that I know many young people whose parents made a different choice, and who fared perfectly well. My children attended the local state primary, and when I hear how some of my elder daughter's comprehensive school friends are doing at university, I have wistful thoughts of foreign holidays that might have been. But I also know of clever 11-years-olds who didn't do so well. Kids from decent, hard-working and supportive families who would certainly be in higher education had their parents been able to pay. I was unwilling to leave things to chance - even if the odds were pretty favourable in our well-heeled catchment area.

Why go down this road? I have unpleasant memories of school, especially the peer pressure to under-achieve. I remember the fear at break time, the jostling, the obscene abuse from boys, the spitting, the atmosphere of aggression. You had to work hard to restrict your conversation topics and your vocabulary, and never, ever make eye contact with someone who wasn't already a pal, lest you be challenged with the menacing “What the f***are you looking at”or the only slightly less offensive “D'ye want a picture?” Eye contact is the primary, nonverbal way human beings connect with one another. To be threatened by it reveals a low sense of self-esteem. So it was the damaged kids - a minority - who set the social tone. They say it prepares you for real life - but what life? I cannot say it provided the confidence to, say, interview a first minister or address a roomful of strangers - those were skills I learnt much later.

Champions of the comprehensive system often complain that children only fail because of their family's existing social problems, and pupils whose parents are encouraging will do well at any school. This is manifestly untrue, because it ignores the considerable social influence exercised by the boorish and bored.

We had good teachers at our school, and because streaming was still in vogue, there was a level of protection in the classroom that is not enjoyed in these mixed-ability times. The Sunday Times story today about a decline in standards at the prime minister's old school, Kirkcaldy High, reflects a similar shift in approach. When Gordon Brown was there, bright children like him were fast-tracked.

Mixed ability is a menace that consistently makes children go backwards in the first two years of secondary school. I regularly meet teachers who complain that keen children suffer from being among those who do not wish to learn. Research commissioned by the Scottish government two years ago found that teacher morale was ground down by constant, low-level bad behaviour. Teachers said a third of their lessons were disrupted some of the time. Of those questioned, 27% experienced “calculated idleness” several times a day, while 28% had to cope with “general rowdiness and horseplay” during lessons more than once a day. This will not be helped by the increase in composite classes, another bad news education story we reveal today.

Of course some young people successfully resist both pressure and distraction. I remember them being called snobs and swots, of being bullied and generally keeping their heads down. By choosing private school, my clever daughter was able to excel academically without feeling like a freak. Her friends were all doing just as well. Yet it was no killjoy, academic hothouse. Not a moment was wasted - free time was spent playing sport, music, or fund-raising for charity. There was a culture of excellence, of the celebration of individual achievement that is still too often absent in the state sector. This is particularly true of mathematics and science, which everyone agrees hold the keys to our nation's economic wellbeing. These are difficult subjects that require rigour and application. Many state schools struggle to find teachers for them and are too distracted by their many social obligations to give them the focus they demand.

The debate about education in recent years has been essentially concerned with pulling up underachievers. Problematic children don't just disrupt the working day of teachers and other children, they grab the attention of politicians, educationalists and commentators like myself. There is endless talk of making lessons more relevant and interesting, or teaching bricklaying and hairdressing. How much time is devoted to ensuring that we increase our A grade passes in higher maths and physics, or setting targets for chemistry?

I suppose this exposes the dichotomy for well-informed and ambitious parents. Scotland is an urbanised society in which poverty is acute. The number of young people “not in education, employment or training”, the so-called Neets, must be addressed. That Scotland has the highest number of such teenagers in Europe is shameful. But what of those children who require stretching, and the sort of teaching that will help them achieve their potential? Until the state sector can deliver for both groups of children, I do what I think is best for mine. And that's the best I can afford.

joan.mcalpine@sunday-times.co.uk

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