What does this progress 8 score mean?

[36and3]

Other than I get they're doing well but what does it actually mean in layman's terms? It's our nearest school and most likely dd will get a place for September. It's an all girls though which does put us off. Otherwise oftsed outstanding for the past few inspections.

"But the question was “why is a perfect score at SATs and a perfect score in GCSEs not 0 progress” the answer is that it’s relatively more difficult to get a perfect score in GCSEs"

Technically I think the question was "why is a perfect score at SATs and a perfect score in GCSEs not 0 Progress 8”. The Government has no measure for absolute "progress".

The answer is that some children with lower SATs results also get perfect GCSEs (so have higher Progress 8) and some children with perfect SATs get worse GCSEs (so have lower Progress 8). The only scenario that would give this child a P8 of zero is one where every child who got perfect SATs also got perfect GCSEs.

In other words, an individual child's P8 score doesn't just depend on how well they do, but also how well/badly everyone else does. It is a relative measure, for judging schools against other schools.

Progress 8 isn't a measure of progress, it's a measure of "relative progress". It's used to measure the performance of schools compared to other schools whose children got similar SATs results.

But if that is the case why the definitions include the word progress and they do indeed describe it as progress made between KS2 and GCSE

Progress 8 in grammar schools is very difficult to understand

“why is a perfect score at SATs and a perfect score in GCSEs not 0 progress” the answer is that it’s relatively more difficult to get a perfect score in GCSEs

It's actually just an artefact of statistics when you put a ceiling on scores, such as 120 for SATS or 9 for GCSEs. Some PPs had it right that negative noise (kids having bad days) bring down the Attainment 8 scores while positive noise (kids having good days) can't bring them up, even if they smashed through the 9 boundary on the GCSEs.

I think that we write here about the meaning of Progress 8 if SATs were at max 120 and not debating the value of it. @user149799568.

Well the short answer is that you can't talk about relative progress without using the word progress.

Another answer is that there is the official Government definition, and then lots of informal explainers, some of which muddy the water, so it's best to stick to the Government definition.

The Government definition says P8 "aims to capture the progress", not that it is the progress.

Top coding causes problems in both directions. Superselective grammars may select children who would have averaged well above 120 on the SATS if the scores weren't limited to that level. The attainment of these "super-120's" is then compared with that of all 120's.

"Progress 8 in grammar schools is very difficult to understand"

No more difficult than any other school.

P8 compares the attainment of children at each school with other children who got similar SATs scores at state schools nationally. Most high attaining children in state education are at non-selective schools, not selective schools.

If a grammar school has a P8 of 0.5, and the comp next door has a P8 of 0.5, then, in principle and on average, a child who was high attaining in their SATs should do equally well at both. (Whether they do or not obviously comes down to a range of local and personal factors).