Don't believe a girl can be 'over-tutored-if tutors could magically give powers to pass the exam on the day to someone not able to cope with the work they could bottle it and sell it - just an urban myth.
I disagree. My background - Grammar pupil at Dorking many years ago, daughter in Y7 at local Grammar (in Gloucestershire), Appeals panel member for local grammars (and also primaries). I also have many friends who are teachers in Grammars.
At appeals we sometimes get children from prep schools who have been given practice papers and tutored for well over 2 years (one school used to boast that it had 100% record of 11+ passes), yet they've failed the test - sometimes just by 1 question, which still appears to make them pretty bright - yet then we look at other academic indicators - VRQ tests set by the school, CATS, Ed Psych reports, and these children are often pretty average - ie the midpoint on the IQ chart. They have been over-tutored to pass the test because parents think that Grammar will be the best education for them. Well, in these cases, it's probably not. They would struggle with the work, will need more attention from the teachers... A good comp, or private school (which are often effectively comprehensive apart from parental income in intake) would be much better for the child.
Talking to teachers (not at the schools I hear appeals for), they can't pick out children who get through on appeal, but can pick out the ones who have been over tutored.
In my first year at school, there was a really nice lad whose parents had sent him to prep school, and also had him tutored a lot to pass the 11+. It was so important to the parents that he went to a Grammar that he had to spend 1 1/2 hours each way travelling, including a change of trains. Yet he struggled like mad to keep up in all lessons (apart from PE, which he was good at). Eventually the headmaster wrote to his parents and asked that he leave the school, saying he would do a lot better in a local non-selective school where lessons could be pitched at his ability.