Fiona:
first off I think you have to think through what the 'issue' is for you:
reading skills
writing skills
calculation skills
For Year R/ Y1 - I would highly recommend OXFORD OWL: help in both maths & reading: www.oxfordowl.co.uk/for-home/ - lots of free e-books as well. Lots of advice for parents to support reading skills and phonics.
For learning how to sound out: Find out what phonics package your school is using and look into support materials. For example Jolly Phonics does a lovely series of 7 workbooks working through the various letter sounds/ letter combinations - but it's laid out like a colouring book and includes 3 line writing practice (including instruction on how to form letters).
With reading: joining your local library/ regularly going to the library/ regularly reading/ swapping books with friends/ buying in books/ encouraging family & friends to give books as presents - but read, read, read - regularly is a huge benefit.
Also don't be snooty about reading material - it doesn't just have to be a book. There are lots of children's magazines out there - related to popular children's tv, etc... with lots of puzzles, maths, reading work tucked away - none of which feels like work.
Audio books are fabulous - as is you giving your DC a night off and just reading to them. I used to let DDs read their guided reading book 2/3 nights a week (we only changed books once 1 week/ sometimes once a fortnight) - and then reading something they enjoy/ want to read/ or old family favourites.
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With maths & generally homework help/ ideas:
Woodlands Junior School Resources: resources.woodlands-junior.kent.sch.uk/ - their Maths Zone is fantastic!
There also is a free on-line maths games (organised by age ranges 5-7/ 7-9 and 9-11) called Maths Champs: www.mathschamps.co.uk/#home
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Lots have posted on MN about on-line maths tutorials - so just search on that. My advice is decide if this is an issue - rather than 'double up' whatever the school is doing.
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Finally - look into the resources the school may be providing.
My Maths (for example) allows you to do more at home (TOTALLY FREE) using the 'LIBRARY' - you can work out what level material you're child's teacher has been assigning and if you want to do more/ or just review something/ do something again - you can. There's nothing stopping you.
If your school belongs to something like Education city - again - there's lots of age appropriate games there too!
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having been there and done that (DD1 Y7/ DD2 Y5) my advice is try to get a sense of where there may be problems/ weakness - and work on those at home.
HTH