I used to be in charge of y 7&8 Maths and I wouldn’t agree with everything people have written above, points made,
It’s good that the school have systems set up to help students who are struggling from year 9 onwards, but not much help for you at the moment.
So, you are generally happy with the school. What does your son think? Is he worried?
You say he’s not performing well in Maths and Science. Is he doing a lot better in his other subjects? How does he think he’s doing - does he tell you he doesn’t understand in class?
Just knowing he got 57% isn’t particularly helpful. It might be for his last test, his mark in last year’s exams, the average of his marks for class work or prep, for example. Is it unusual for him - what marks was he getting last year? If you were given the average and the range for his class, and possibly his year group, as well, so you could see how well he’s doing relative to them
After I retired I went back into school to tutor students who needed extra help with their Maths. In my case it was mostly students who had specific learning difficulties, for instance dyslexia - I am trained to teach students with dyscalculia. Either school paid for this or parents did, depending on the circumstances. You could ask if there’s anyone who can tutor your son in school, for which you would pay. It might be unusual but that’s not to say it’s impossible.
I’m not sure how helpful predictions for GCSE are at this stage, but it might be helpful if you can look up the school’s past performance in GCSE Maths and the Sciences. I didn’t teach in a particularly selective school, but I can’t remember a child who achieved less than a 4 in any subject.
Does the school have a big intake into year 9? Did he join in year 7.
Especially when you don’t see him every day, it can be very concerning if son is doing less well than he could, and I understand your wanting to help him with this.