JET11:
The teacher has claimed the homework she is witholding from your DS is too tricky and I'm afraid you have to abide by this. My solution would be to ask the teacher what targets for maths he's working on and then find on-line resources or APPS to help support that.
My experience was a school which initially would claim weekly homework at the start of the school year, and then would forget all about it. We've also had serious problems with DD1 getting math concepts during her time in KS1 - so we've gone it alone at home.
Many here have written about the on-line tutorials (myself included) - Mathswhizz (www.whizz.com/), Mathletics (www.mathletics.co.uk/ or mathsfactor (www.themathsfactor.com/). I think all of them offer either free trials or first month of tutorials at a discount. All of these will assess your DS and start from where he's at.
I was personally concerned about how maths was being taught (which seemed disjointed - i.e. in mid Y2 DD1 had a good grip of fractions (1/2, 1/3, 1/4 & 1/8ths taught by trainee teachers) but couldn't subtract 1 from 10, which struck me as odd). School was less than helpful so we went our own way and have never looked backed. DD1 has improved beyond recognition and securely knows how to add, subtract, multiply & divide - which was our aim.
If English is the weakness - than really work with him on the homework - try and ensure he avoids shortcuts and really discuss/ target problem areas. For DD1 its vocabulary - so when she reads to me whilst DD2 is having her bath with DH, I'm constantly saying what does this or that word mean. It's slow going, but there is a noticeable improvement in the range of vocabularly (certainly an increase in >2 syllable words in use now).
Some really useful websites for maths:
Coolmaths www.coolmath.com/
Woodland Junior School Maths Zone resources.woodlands-junior.kent.sch.uk/maths/
Table trees (multiplication practice) from ambleside primary: www.amblesideprimary.com/ambleweb/mentalmaths/tabletrees.html
Coxhoe primary numeracy links durham.schooljotter.com/coxhoe/Curriculum+Links/Numeracy/
BBC Bitesize KS1 SATs numeracy practice: www.bbc.co.uk/bitesize/ks1/maths/ - also offer practice in English & Science.
BBC Learning - has games/ worksheets related to maths at KS1 here: www.bbc.co.uk/schools/teachers/keystage_1/topics/maths_ks1.shtml
BBC Learning is in general just a really nice resource to get additional materials in subject areas (link here: www.bbc.co.uk/schools/teachers/) - select appropriate tab KS1 or KS2 in orange outlined box at mid left of opening page and then select the appropriate area of the curriculum. It takes a bit of exploring - but there's all sorts of great stuff there. Very useful when suddenly presented with a topic like research about Roman Army and not sure where to begin.
HTH