It's all rubbish.
I went to a top boarding school that was boys only until 16, then a small number of girls in Sixth Form.
None of that stuff went on.
Times have changed a lot since the 1950s. There is no longer the strict hierarchy in boarding houses; yes older boys/girls are respected, but they would never abuse the younger ones in any way.
Additionally there are far more socials with neighbouring girls' schools than 50 years ago. Schools (both boys and girls) recognise the importance of social events now, far more than in years gone by.
Boarding schools are ENTIRELY different establishments to what they were even 30 years ago. For the amount of money parents pay (upwards of £25 000 a year for the top schools) a very high level of pastoral care is expected. Masters are no longer figures to be feared, but teachers who play an active role in ensuring every boy or girl in their house is happy. In the 1950s getting a warm shower would be a luxury; nowadays by the final year of Sixth Form you have your own room, and sometimes an ensuite.
I've read reports and diaries from my old school from years gone by, and there are few similarities between the establishments. Sure traditions remain, which are important parts of the school, but the overall ethos is totally different.
Finally - most parents who send their children to boarding school went themselves. If they were soooo traumatised by all the gay sex, why would they put their sons in the same position?
They wouldn't. It's all rubbish and anyone who goes/went to a boys boarding school would scoff in your face at the remarks.
Ultimately the top boarding schools provide a level of education incomparable to most schools in the UK - they are lengths ahead in terms of academics, pastoral care, facilities and opportunities on offer. Sure you pay for it, but it is so worth it.