There's another thread, sorry, I can't find it, that lists the words that the National Curriculum wants them to sight-read, sorted by which term in Yr-R that they focus on those words especially. Here's the list (I copied & pasted it for home):
Term 1
I my me a no
he in mum dad the
to am it of she
Term 2
at yes can see we
up is go and on
for said cat all get
Term 3
look you like went are
this going they away play
come day big was dog