I have mine at their tables. They can all see me and I can see them. If they need resources, to write on mini-white boards, show me with number fans, play bingo, they are all handy and easier to manipulate. I don't sit my KS1 class on the carpet very much. I have a rather small classroom and the carpet area is small, so I don't like them all squashed up together. I certainly don't like sitting on a hard floor, in a confined space with other peoples' elbows in my face, so why would the children?