From the Government document about secondary measurements including progress 8:
“There will be some pupils (those arriving at secondary school from the independent sector or abroad) who have no key stage 2 results to use as the baseline for the Progress 8 measure. These pupils’ scores will not be included in the Progress 8 measure. “
Source:
https://assets.publishing.service.gov.u ... th_ref.pdfWhen you look at the fine details on the compare schools tool of number of pupils who took exams and number included in measure it can give a rough guide of those who were not previously at state primaries. Some of course may have been removed for last term of Y6 so as said just an indication but an indication nonetheless.