Good luck to everyone. A year later and it is all over and both kids (11+ and 13+) are happy and settled in their new schools.
London days schools at 11+ are a real lottery, and produce some strange results. Much of it is a numbers game and not getting a place should not imply rejection, though it is hard to feel otherwise.
We were in the same position as MrsHighandMighty in that no school was a given, so DD tried 5. We were lucky in that we had a fall back of staying on the previous school, so were able to take the approach that every school we applied to was a school my daughter wanted to go to. We therefore tried not to think about which one we preferred until we knew what choice we had. The prospectus cannot tell you where you will find the best-friend-for-life or the inspirational teacher, and every school, including the most academically sought after, will have a few amongst its cohort who find it hard to settle.
We did not try St Bens as it is a bit far for us. However we do know a lovely girl who started in September and who is very happy there. My own daughter is enjoying the switch from a very academic prep school to a less hot house environment with lots of sport and is far happier.
In terms of interview, I was told, by an interviewer, that they are really looking for a child who can talk to adults and who has something to say. What they say is less important! It can be obvious which kids have been coached, and they can come across as very dull.
If a child does not get anything when they should have, and it does happen, you might talk to your Head Teacher, assuming they have good experience of the process. (Or firing off some careful letter to schools at which your child got an interview, or others you failed to consider which might be easier to get into.) Year on year schools go in and out of fashion. In the next few weeks schools will find out whether they will have to add an additional class or whether they will be going through their wait list too quickly. (However don't expect the latter to happen to really competitive schools like CLS. Too many parents will be prepared to ditch their previously accepted school and lose a terms fees.) A Head Teacher may be in a position to ask this question, and also confirm that your child would fit in well within the cohort.
If you are writing I would couch it in the form of an enquiry about an occasional place. These do come up, and can be from the start of Y7, and though they cannot make promises, schools may want to encourage good prospective candidates.
I am so glad it is over. In the end all my daughter's friends got schools they were pleased with. I hope the same is true for everyone here.