There are 2 different sorts, both are attributes of polygons. Have students sort with no directions from teacher. They should not glue until you discuss the real attribute being sorted.
*One is for them to sort curved and straight sides (vocab words are attribute: something you can observe & curved: a line that is not straight). The other is for them to sort open and closed figures. (vocab words are attribute: something you can observe & closed: completely connected; the end and beginning meet.)
(boy and girl clip art by creative clips:)