Progress 8 - adjustable for cohort stability?

[ablyhandled]

A school we're thinking of applying to as first preference was undersubscribed when it first opened a few years ago, but now is oversubscribed with a really good reputation.

The year group that just did its GCSE's was one of the undersubscribed ones back in Year 7 - by about 30% - but I've been told it grew over the years to be almost full, taking in kids who've moved into the area or who have moved from other schools - either because of the school's reputation or sometimes because they were having troubled times at other schools. Some of them just joined the school in year 10 and 11.

The progress 8 result was below average, but is that likely to be because it measures progress from Year 7 and it includes everyone, even if they came from another school fairly recently? Is there a way you can get an adjusted Progress 8 score of just the kids who've been there since Year 7? From everything else I've heard it's a really good school.

And am I missing something or does this Progress 8 thing just encourage schools to kick out their underperformers before they do their GCSE's and discourage other schools from taking them in?

30% is a heck of a lot to have to deal with but if they had places empty from Year 7 they would have had every excluded child in the city moved there. No wonder their Progress 8 is low.

On the plus side if the school is now over subscribed that negative data will disappear as soon the first full year gets their GCSE results. The head will have the data for just the Year 7 children there from the start, so ask just ask the school for it. If its got a good reputation then it must be doing something right, local parents usually know a good school.

Last year's league tables included the result for the 'non-mobile population' A*-C. I don't know if a similar figure will be included for progress 8 once the full tables are out, but if it was there before, they must be considering including it again.

noblegiraffe, where would you find this 'non-mobile population' A*-C 2015?
Have looked, cant see it

anon it's well hidden. I found it by going to a particular school, selecting 2015 data, then clicking on 'compare with similar secondary schools' (at the top just underneath the school info and address, Ofsted rating and useful links). The last column on the school comparison table is the percentage of non-mobile pupils achieving 5A*-C.
I don't know if you can see it anywhere else.

Found it, thanks nobelgiraffe. But it only covers Y10/11 so won't explain what happened to the children who were in the school for 5 years. And in this thread it seems an exceptional number joined through out the 5 years.