Thanks all for the suggestions. I think I'll give the rods a miss. She already has regular wooden building block, duplo and pattern blocks. I think each of those lend themselves better to exploring/ playing/ discovering/ natural learning than the rods. Much of what I've seen about the cusinaire rods is about specific instruction and the comments here have confirmed that.
I'm interested in the comments that many of you said about not needing concrete representation of mathematical concepts and 'just knowing' them. I recently read a paper which found that for children who do understand abstract concepts, that physically representing them with rods etc can actually be limiting. I wish wish wish I had written it down - I have no idea where I read it now and I can't find it again.
If you find that paper let me know, it's exactly what I have been trying to explain to school about my DD!
