DD's school gives school target (aspirational) and 'working at' grades. However, the aspirational targets are adjusted and are set conservatively. DD2 in Yr 9 for instance has 6 across the board for all her targets. DD1 at this stage was targeted all Bs except in History where she was targeted an A. This was downgraded later and the teacher told off. I strongly suspect OFSTED gaming going on.
Targets have been adjusted each year so by mid yr 11 DD1 was targeted 8/8/8 for both Englishes and Maths and A or A* in everything else. This is pretty realistic, though she's struggled with Chem and Physics coursework (far prefers terminal exam system). She won't be far off her target.
DD2 meanwhile has already exceeded about half her current targets - I expect to see those adjusted come September as she is working at a 7 in Geography, French and English. It still isn't an exact science, but I do have some faith in the school's predictions.