A circle chart allows students to think about what they know on any given topic. This organizer encourages students to think about what a concept "is" and what it is "not'! Students will write the topic in the middle circle (such as, the Civil War, nouns, equivalent fractions, three states of matter, sentence fragments, etc.) and then in the outer circle they write their thoughts in words and phrases.
This could be a quick formative assessment to gauge what students have learned about your lesson. This can then guide your instruction by knowing who needs a better understanding or who needs to go deeper.
I liked having a set of copies of this chart ready to go and to use at any time. Great tool to use during an evaluation! The preview is a screen shot of part of the complete map.
** If you like this formative assessment strategy, you will like the others that have listed.