Hi SarfEasticated:
Mumsnet explains National Curriculum Levels here: www.mumsnet.com/learning/assessment/national-curriculum-levels - read this & then follow the links (related pages in blue boxes on right) to other information on how you progress through the NC levels whilst in primary school.
Basically the end of year Target for Year 1 is NC L1a according to mumsnet (see progress through NC Levels chart at bottom of this page: www.mumsnet.com/learning/assessment/progress-through-national-curriculum-levels
So your DC (only 1/2 way through year 1) is doing just fine - maybe a little low for maths.
So what you could work on in maths is ensuring that your DC really gets counting: to 100/ by intervals of 2/ by intervals of 10/ by intervals of 5
Understands even and odd numbers (read door numbers going up your road - walk up one side & down the other to cover evens and odds - great to do on the way to school/ park/ friends/ etc...)
Gets number bonds to 10
Presuming that they get the ways to make numbers 2 - 4
so all the ways to make 5: 1+4/ 2 + 3/ 3 + 2/ 4 + 1
make 6: 1+5/ 2 + 4/ 3+ 3/ 4+2/ 5 + 1
make 7: 1 + 6/ 2 + 5/ 3 + 4/ 4+3/ 5 + 2/ 6 + 1
etc... to 10.
Play games like snakes and ladders - forward for counting up (add a second die so you can count up to 12) and backwards for counting back.
VISIT Oxford Owl early maths page - which has lots of resources/ games to support learning first principles in maths: www.oxfordowl.co.uk/for-home/maths-owl/maths
Encourage real life maths:
Measuring things for cooking
Dividing things (pizzas/ cakes ideal for this) into halves/ thirds/ quarters/ etc...
Discuss how best to be sharing things out - another way of thinking of dividing - so you have a bag of 15 sweets but there are four of you at home - but you want to give the same number to everybody - how many would that be. How can we work it out (encourage 4 piles).
Again - don't be too worried - see it as the school indicating to you where your DC's strengths and weaknesses are. It's good to know they're a bit weaker in one area - it helps you to focus on things at home.
Also - don't be shy. Ask the teacher (if you haven't already) what you could be doing at home right now to help with your DC's maths. It may be it really helps.
HTH