Rhiannon Harries: Look closely at boarding schools and 'Cracks' in the fantasy soon appear

Trying to explain your home nation's cultural peculiarities to an outsider is the best way to gauge the degree of their absurdity, as I found out the other day when a French friend asked me what exactly Eton is. "Well, it's just a school really..." I began, before launching into a labyrinthine explanation of how it was actually much more than just a school. I covered tailcoats, rowing songs, Gothic architecture, 18 British PMs (not by name, obviously – I'm not that good) and a recipe involving broken meringues.

My friend, never having been to boarding school nor known anyone who had (they are few and far between in France), was baffled but impressed: another victim of boarding-school fascination. Many more will no doubt be similarly afflicted this week as Jordan Scott's directorial debut, Cracks, plays at cinemas. Set in a girls' boarding school in the 1930s, it's all meaningful glances and, er, Gothic architecture as it traces a Sapphic love triangle involving two pupils and their charismatic teacher.

How private boarding schools still survive is a mystery. Not because they are ventilators for a brain-dead social hierarchy – the same could be said of any fee-paying school – but simply because you'd have thought that every portrayal of boarding-school life, from tabloid exposé to Enid Blyton, would be enough to scare off either the parents of prospective pupils, or the pupils themselves. At one end of the scale are fictions such as Cracks and sensationalised reports of sex, drugs and general depravity amid the cloisters. At the other are the jolly-hockey-stick Harry Potter clichés.

Send your child to a boarding school and they won't have any time for GCSEs because they'll be too busy either casting spells or dealing crack is the take-home message for parents. Likewise, are kids today really suckers for dorms, school songs and (shudder) school on Saturdays?

Yet I, too, spent a large part of my tween years dreaming of being packed off to some creaky Hogwarts-style castle – before means allowed me a brief sojourn in the dorms. It wasn't so much of a shock as a mild disappointment. The truth, from my experience, is that no more intrigue takes place in boarding schools than at any other school or workplace – it's just that as it takes place on the premises, it never stays secret.

Of course, the crucial factor in sending a child to a boarding school is simply that they are, by and large, endowed with superlative academic and sporting resources. I was efficiently transformed into a super-swot. Not in the least bit sexy, but then that is probably why so many of those with first-hand experience are more than happy to let the hilarious fantasies stand.