I’m shocked that you’re shocked at this. I mean, I didn’t grow up or go to uni in the UK. I have lived in 3 other (non-European) countries and I would say it’s exactly the same in other places.
In my home country, I’d say class is even more entrenched, but less openly acknowledged. If you grow up in a certain family in a particular area, you are expected to go to a certain university and you will join only certain social clubs there. There are universities that you pretty much only go to if you have a certain (minority) ethnic background. Growing up, we knew not to go to parties at those universities or even step foot on the campus because they were deemed ‘unsafe’.
There are very much universities for the elites, those that are more middle of the road, and those that are just holding pens for minimum wage workers. Even if you are poor or working class and go to an elite university (and many do, I consider myself very middle class now but come from a working class background, I went to fairly elite universities and got a PhD), still you needed to know how to ‘pass’.
British people are obsessed with class, but it’s really not a British thing at all.