It is a grammar school and that, of course, will mean that there will be pressure to do well - and a lot of this pressure will come from the girls themselves.
That said, after visiting AHS, Dr Challoners and Beaconsfield High in the last round of open days (we were considering moving house), AHS was by far the least pressurised and most relaxed of the three. I actually thought the girls there were very down to earth and a lot more "real world" than at the other two schools. They also seem to have a healthy relationship with the boys school, particularly in the sixth form, which to us was quite important.
I could really see my daughter there but not at the other two schools. I am, perhaps rather naively, very anti tutoring though. Sure we'll do practice papers at home to familiarise her with the style, concentrate on speed and accuracy, but this is exam technique. If she can pass the exam without formal tutoring then I would feel very happy about sending her there - it's a great school. I would, however, worry about her being able to cope there if she scraped in.
Three of my friends send their daughters there - one very gregarious and outgoing, three very kind of "normal" and one wouldn't say boo to a goose. All are very happy and doing well.