Thumbs up is not Formative Assessment

Thumbs up/Thumbs down is not formative assessment. At best, it is a test of the waters that isn't very accurate. Formative Assessment is about learning what the kids know and don't know and then using that information to adjust instruction. By the way, remember that it isn't graded. Check out my link below for some great formative assessment resources.
https://www.pinterest.com/smiletto/assessment-strategies/