any suggestions where I can find these? I was asked to teach 4 3rd grade classes in a public school. Just need some ideas to get things going. Thanks!

Search youtube, but to get you started....

Polka, Greek dancing (they do it in a circle), Line dancing/square dancing, russian cossack (for the boys), flamenco or paso doble style if a lot of boys, and African dance.

Have fun!! I love teaching ethnic dances...