To send DS to private sixth form or not?

[ChampsNCanape]

In the town I am living in there are two sixth forms - one is independent and the other is a state school. The state sixth form is good and is rated 'outstanding' by Ofsted, and they achieve quite high A-level results as well (comparable to some cheaper independent schools in the local area). The independent school has excellent results - probably about 15-25% better than the state school however it is also quite expensive (even compared to other independent schools), it is £35k per year for day school and that doesn't include uniform, food, trips etc.. We can afford it however wonder if it is necessary.

Honestly wouldn't bother with paying for sixth form if decent state available.

If the state sixth form is good near you, I would consider it. I think it does depend on the subject though. A lot of state schools have issues with recruitment and retention of good maths and science teachers. May state schools are less good at these subjects and have lower entry requirements for these subjects too than a private school. If they can't retain a teacher or the teacher goes off sick, it is more of a problem to replace them than in a private school. Consider what your child is planning to do at A-level and whether you were impressed by the subject teachers when you met them.
I am trying to get my son into a grammar school for sixth form which is far away. Acceptance is based on average GCSE score and distance. If he doesn't get in, I have applied to a private school. I am debating whether to put a £1000 deposit down or not to retain the place because I don't know what my son will get in his GCSEs for sure. I don't know whether I should take the risk and just see whether they have a space after the GCSE results. Any opinions? We don't live in London and it is not an oversubsribed school.