smoochypoo
I suppose the question is whether you understand (via the school) or know instinctively that your son is doing well. This is sometimes very difficult to gauge - the school can give you the impression they work to the highest possible expectations and many children pass the 11+ only for a parent to then discover that in fact those children that pass the 11+ have had all sorts of support at home/ extra tutoring that they were completely unaware of. I've just seen this scenario play out with a friend of mine who's devestated to be sending her DD to a school she'd rather not for senior school.
So - I'd advise examining the contents of the draft national curriculum and treating it as a checklist. Look at the contents of the Y5 curriculum documents for english, maths and science and literally go through and tick off the ones you're confident your DS has mastered.
Draft national curriculum English: media.education.gov.uk/assets/files/pdf/d/draft%20national%20curriculum%20for%20english%20key%20stages%201%202.pdf
Draft national curriculum Maths: media.education.gov.uk/assets/files/pdf/d/draft%20national%20curriculum%20for%20mathematics%20key%20stages%201%202.pdf
Draft national curriculm science: media.education.gov.uk/assets/files/pdf/d/draft%20national%20curriculum%20for%20science%20key%20stages%201%202.pdf
If there are a lot of gaps then my advice is to do more at home.
Some things you can consider to supplement learning at home:
use resources on BBC Learning [beta] website: www.bbc.co.uk/schools/teachers/ - just select curriculum topic in orange box for KS2 tab and there's a wealth of worksheets & games to help at home.
If maths is very work - consider joining some form of on-line tutorial (mathletics/ Mathswhizz/ Mathsfactor/ etc... - lots out there to chose from - ask around or try free trials).
If reading/ vocabulary or comprehension are week - consider joining a library and really getting more reading going on at home. Try 11+ practice books in English (very good for really identifying weaknesses and lots of comprehension practice).
But basically as others have advised if your DS is doing well or even above expectations - then relax and just accept that from Y7 you need to help foster a homework routine. My personal advice is make sure there's a nice snack available and somehow snacking and doing a bit of homework doesn't seem so bad.
HTH