I have 2 children at Charterhouse and do not recognise some of what has been written above. The school places emphasis on the academics and boys have to pass an entry test and interview; regular reports/grades are posted online for parents and are discussed with tutors.
Outside the classroom, the standard of sports is very high (it obviously varies from year to year - but, for example, one cricket A team was unbeaten, seeing off Eton, Harrow, Radley, Wellington, Tonbridge etc). It is a football school so size need not matter in the same way it does at the rugby-playing schools. Pretty much every sport you would want is on offer, with ex-international players coaching major sports.
Pupils are also expected to engage in a wide range of artistic and cultural activities and there is an impressive choice of societies to join. Again, these activities are discussed with tutors in regular meetings.
Some pupils are from very wealthy backgrounds, but most are from the more traditional public-school background (still relatively well-off, of course). Geographically, most are from the Home Counties and London, with some foreign students (although no more - or fewer - than most similar schools I'd say).
There is a new HM who seems to have hit the ground running, and the school will be 1,000 strong when fully co-ed in a couple of years - rather than reducing the number of boys to make space for more girls, the school is building new houses to accommodate the extra pupils. The boys seem to be looking forward to the arrival of more girls.
The house system is strong, with houses varying in character depending on house-master and reputation. Though some of the 1970s houses do not look great from the outside, they actually work on the inside and the fact they are located near each other encourages inter-house friendships. The main school is one of the most beautiful you will find, and the cricket and football pitches cannot be bettered.
Socially, there is a lot going on, in and out of school. Discipline is strict - and they are super aware of any bullying. Pupils are also made aware of how lucky they are, and engage in social programmes.
All in all, a pretty impressive traditional but forward-thinking school. Pupils are kept on their toes and, from what I have seen thus far, turn out very rounded and very well on the whole. My hunch is that the school is going from strength to strength, and will be even harder to get into once fully co-ed.