I remember having Cuisinaire rods when I was young, in the 60s. I don't think we had them at school, I think they were pretty new, at least in the UK, and I'm pretty sure one of my parents got them through their job (they were both schoolteachers).There were a couple of times in primary school that I remember learning something about math. The first was when we were given different sized containers and allowed to play filling them up with water. Didn't take long to understand how volume worked. The second was when we were given Cuisenaire rods and allowed to play with them. That's when the penny dropped for me on math.
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Now you've mentioned them, I wish I'd got them for my kids, and then for my grandkids, but it's probably a bit late for even the latter now. However, I think the resources for kids are much better now, and the Numberblocks series on BBC TV conveys much of what you get from playing with the rods (though obviously not as physically). https://en.wikipedia.org/wiki/Numberblocks