"Junie, you are wearing a dress. Sit like a lady!"
I love hearing students repeat my words. It gives me a special kind of feeling and lets me know they actually listen to me.
The kids in my class are required to sit "criss-cross-applesauce" when we are on the floor. The only exception to this is "ladies" wearing dresses/skirts who are required to sit with their legs folded to the side ("like a lady").