This is a difficult one to respond to.
First of all a waiting list is ranked (ordered) on the basis of the admission criteria for the school. Its made up of the unsuccessful applicants to the school, those who were unsuccessful in the first round, which means in practice those who lived too far away to get an offer up front. However anyone who was a late applicant in an area can (have to really) go on waiting lists; also anyone who has not been allocated a place for any of their preferences (or not allocated a place they have decided they want), will if they read the advice on Mumsnet (!) be putting themselves on the waiting list for any acceptable school..
So you can go down the ranking because someone who lives closer to the school adds themselves.
However, this does mean that children will often appear on lots of waiting lists. So what will cause you to move up is:-
- Parent decides not to accept place at your first choice school. They may be in the process of moving out of the area, one of the couples gets that dream job offer somewhere too far away, or they take up a private option.
- Child before you in the ranking gets an offer at a school acceptable to parents and therefore goes off all the waiting lists they are on.
So this means that, at the moment there needs to be at least one vacancy at your first choice school and the five on the waiting list ahead of you need to get places somewhere, not ness. at your favoured school.
So what are the chances?
This depends partly on how many forms of entry there are, as the bigger the intake, the smaller the percentage shift needed to get you in. But other than that just depends on the number who drop out and that will vary a lot from year to year. Also, and this is the nail biting thing, the school will not know for sure who is coming until a couple of days into the autumn term! Some parents will just not turn up. So you might get an offer at very much the last moment.
With a two form entry school from my experience being 6th is hit and miss; you do have a reasonable chance, which you would not, in my view have if you were say 15 on the list, but you dont have the very good chance of being say 2nd on the list.
I hope this long posting helps, I know it is really hard for you that no one can be more definite.