Boarding school is very much not a general UK cultural thing - I went to the local comp, and so did everyone else I know. It is a class thing, specific to a very niche sub-section of the population: the rich. Historically, I believe, it stems from an age where there were very few local schools, so the wealthier families, because they could afford it, would send their sons away to be educated. And that also ties in with a lot of snobbery around not wanting their kids to mix with the lower classes (bearing in mind that most of the kids in the district would be lower class), and misogyny around needing to 'break the apron strings' so that little boys wouldn't be too attached to their mothers and governesses, since raising children was women's work with the men not involved, but the men also didn't want their sons to be too 'womanish' as a result of being raised by women, so off to school they were sent. Then, with the expansion of the Empire, a lot of boarding schools were established to cater for children whose parents were overseas in places like India - a lot of Brits who went to work in India really struggled with the climate, so they would send their children home to the UK because they were afraid for their health. And later still, that element of not wanting the 'better class' children to mix with the hoi polloi in local schools continued - and exists to this day. If you read any of the old 'Girls Own' or 'Boys Own' literature set in boarding schools, Enid Blyton for instance, that attitude comes across strongly, with families who considered themselves 'better than' really stretching their finances to the limit to afford school fees rather than suffer the social horror of having their children attend the local school with the riffraff. Boarding school is 100% a elitist thing, all wrapped up with wealth and social status, and only a very small minority of the population ever attends them - which is where, of course, the 'old boys' network begins, on which so many depend for career advancement, which is a big part of how the rich stay rich. It's all about class, and about maintaining a rigid distinction between the classes, making sure the privileged class stay privileged by ensuring that they associate with all the 'right' people and are given an advantage over their more common peers.