Get your entire class involved in your lesson with this smiley and frown face. Your students or you can cut out each face and attach them back to back to a popsicle stick or tongue depressor for choral responses to such questions as True/False, Yes/No, Fact/Opinion, Sentence/Not a Sentence, and many, many more. You might want to print them on a color copier on a sturdy paper and perhaps laminate them. I use these quite often with my students and they go over very well. You can get an overall sense of the class's understanding of a particular concept.