Is there anything which actually has to be remedied by the next term OP? Is someone saying he may have a specific learning difficulty? I’d imagine if there was, it’d be on the report but you could chat to his teacher to reassure yourself. And no need to worry anyway.
Otherwise I would not discuss it with him, he’s little, not a teenager who can benefit from assessing their own performance with specific goals in mind. He hasn’t done anything wrong and he’s not behaving badly. What do you think he or you could do about this nebulous ‘not meeting national expectations’ or whatever at his age anyway.
Children – without you realising it – can take ‘discussions’ about school attainments far more seriously than you would want: at that age it can seem like your love is conditional on doing ‘well’ at school, which is deadly. If he’s enjoying school and participating in it, why would you burden him with a notion that he’s failing in some way. Encourage him to love learning about the world, anything can be a subject for learning.
At university, I come across students who have learned that their worth is dependent on their achievements at school measured narrowly by grades: they can be deeply unhappy young people.
Have a secure, happy and enquiring-minded child instead of worriting about individual school reports.