My husband went to Radley as did a lot of my friends. Our son was also down to go to Radley - however we pulled out just before he was due to take CE as we were increasingly concerned that it wouldn't be right for him (not an academic issue - he's pretty clever - but just didn't feel like a place in which he'd thrive - he's a London boy and being shut in an all-boy environment in the middle of the countryside without access to any shops or girls was likely to be a recipe for disaster). Plus - our prep school head was not particularly positive about them saying that it's not a school for your urban child or gentle soul.
Yes it's a fine school with amazing facilities and regularly sends boys to many of the very best universities and it's also oversubscribed and has expanded in the past few years. So obviously doing a lot of things right.
However - and I think that this is a big however (at least it was for us), it's also somewhere that is pretty rigid and seems to attract a VERY specific type. It's also pretty arrogant.
My godson (son of a former Radley pupil) was down for R. but 'failed' his CE. In fact, he got something like 50% in his English paper i.e. a technical fail - but was fine in everything else and his prep school stressed that this was an aberration rather than a true reflection of his ability. Radley wouldn't take him, wouldn't discuss it with anyone and simply left his CE papers with a secretary for the boy and his father to come and collect so that they could take them to be marked by another school. All very traumatic and upsetting. We've subsequently heard from quite a few people (and unofficially from a few Prep school staff) that Radley has been quietly upping its academic entry level for some time. It's doing this in two ways: 1 - marking harder - i.e. 55% for Radley is more like 60% elsewhere) and 2 - increasing the no. of boys it takes from the Warden's list. The latter is the way of getting your son into the school if he wasn't registered as a foetus.... It's a way of attracting the clever ones..
What this means is that the sort of boy going to Radley is changing. Some may say for the better, but I've been there a lot and the past three times I've been I've been shown round by boys whose first choice was Eton. Worth remembering that Radley and Eton are the only (?) all-boy-all-boarding schools around. My husband says that the feel of the school has definitely changed since he was there.
More worryingly, I seem to hear consistent reports of boys 'taking a year to settle down' at Radley. In most cases, this has meant that they've been pretty miserable and have found it hard to adjust. It's a macho culture with strong hierarchies and few easy relationships between the year groups. In fact, a friend of my son's has recently left Radley citing some pretty unpleasant bullying in his first year from members of the sixth form in his house. Reported it to his HM but despite so-called 'action', nothing has really changed.
Two friends of mine have also removed sons from the school. One after a year (went to Teddies - much happier) and the other after two (day school in London).
Having said all of that, I also know a lot of boys who've thrived there. My advice to you - think v. carefully about what you want and what type of boy you have. In my experiences it's the boys who've a) boarded before, b) come from all-boy prep schools and c) are country born and bred, who've thrived.