I know he’s only 7, but I am concerned about him falling behind
I don’t have any specific advice for you but I will say this.
At 7 years old I was also struggling with Maths, I was also behind* with my reading at that age. I was even a bit crap at maths when I went on to secondary school and for the first year or so there was put a couple of sets down from most of my peers.
But then things changed, the maths became more interesting, the teaching more engaging and I actually started to ‘get it’ a lot more, I wrapped my head around concepts that I had ignored before, not because I couldn’t understand them but because I just wasn’t interested and from then on things took a different turn.
I went on to get straight A’s at GCSE, then did Maths, Further Maths and Physics at A level, and then Physics at Uni and got a Masters too, all involving some of the most horrific maths you’ll ever have the misfortune to encounter, and all from someone who struggled with maths at primary school and shortly after. Obviously your son isn’t me, but he is only 7…
Again, can’t offer any actual advice, but I wouldn’t necessarily worry about the being behind bit of it.
* I’ve since found out that it was mostly due to boredom and the teaching than actually being behind, I had no trouble with language and communication, I just couldn’t be bothered to read the school books because they didn’t interest me, I was a prolific Lego builder and could deal with all the multiples and fractions required to build some awesome stuff even at a young age, but in my head at the time this wasn’t maths, maths was boring sums and stuff.