Please could someone explain what the progress 8 score means for Secondary schools. I have looked at league tables and it refers to this and whether a school is average, above average etc.

I found this, which might be helpful.
Basically, it looks at progress from KS2 results

https://www.google.com/search?q=progres ... mtZsnSYlRM:

Thanks Yoyo123 that was a great help.

As another member pointed out to me, bear in mind that “Progress 8 is not a 'score' but gives a confidence interval - you can't just rank schools.”
However, The article gives a good background into the Progress 8 workings. Another reason why KS2 data is important.