Trying to think back 13 years as to why I wanted DS to go to Reading School...
Partly because his (state) primary school teachers all suggested it, thought he was likely to get in and do well there
Partly because DS was keen - his best friend's brother was there and his best friend was almost certain to get in, and DS didn't like the catchment comprehensive.
Partly because DH and I didn't like the catchment (boys') comprehensive, or its head, either - when the head was asked about bullying, he pretty much said that the only boys who got bullied were 'odd' or 'different' in some way. As DS was very short for his age, I wasn't too happy about his prospects at a school with that kind of ethos. (Having heard from DD what a gay friend of hers went through at that school, I reckon I was quite right. I must point out that that head has now left and I have no idea what the ethos of the school is like now)
We actually put as our first choice the co-ed comprehensive which was next to DS's primary and where about 60% of his classmates went - in those days the grammar application was completely separate. But we didn't live in the catchment and it was extremely unlikely that we would have got in.
When it came to DD, I felt it was worth her doing the exam, though I was much happier with the girls' comprehensive that was our catchment school, and DD actually preferred it - if she had got in to Kendrick, we might have had a hard choice as to whether to send her there or not.
Neither DS nor DD had a tutor, or did more than a few practice papers, and DS's opinion was that the few who struggled in his year were all boys who had been pretty heavily tutored in order to get in.