KS3 to work out GCSE

This is only a guess, but aren't there 8 levels at KS3? There are also 8 grades at GCSE, so I guess you could work it out like this:

Level 8- A*
Level 7- A
Level 6- B
Level 5- C
Level 4- D
Level 3- E
Level 2- F
Level 1- G

That probably won't be completely accurate though, just like using GCSE results to predict A-levels isn't always accurate. You might have slacked off a bit at KS3 but then work really hard at GCSE or vice versa, you might have crap teachers at KS3 but good ones at GCSE or vice versa, you might improve more in certain subjects than others etc etc.

KS3 Sats are by no means accurate evidence for predicting GCSE grades (even though they seemed such a huge deal when I was doing them... ). Level 8 is only attainable through special extension papers or teacher assessment (apart from Maths, where there are 3 tiers and you can get a level 8).

According to that scale and my SATs predictions -

English's - AA
Maths - A*
Science - AA (but I really want an A*! )

You won't necessarily get those though. According to my SATs and teacher assessments, I should have got BB in science but got AA, an A in French but got an A* and a B in history but got an A. Of course, I also should have got an A in maths but got a B and an A* in RE but got an A, which just shows you they can go down as well as up

from ks3 to gcse:

10=a* (you cant get it at KS3)
9=a (you cant get it at KS3)
8=b
7=c
etc.
etc.