What percentage of A*A grades at Gcse should a grammar school be getting

[soul2000]

i have just been on my nephews school website,it says the school got 98.4% 5 A to C My interest though is about the 71% AA the school achieved this was particularly very good when compared next to the supposedly more academic grammar which achieved 63% in the A*A measure.

When you consider that nephews grammar schools intake is 20% middle 80% high ability and that the other grammars intake is 100% high ability
you can see which school has done better.

you can see which school has done better.

How? Are they comparable for which subjects are taken, for example?

I think they both do broadly the same subjects,both schools study 3 separate sciences as compulsory subjects. Both schools top maths sets take maths one year early,both do history and other humanities as compulsory as well as MFL. I think one of the differences though is that at
nephews school they take 10 where as at the other school they take 11 or 12 GCSEs.

It depends entirely on the level of the intake. If lots of kids go in with L6 SATs at KS2 then they ought to be getting lots of A*s at GCSE. It's not really possible to judge overall effectiveness without looking at cohort entry data.