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4th Grade Math – Classifying Triangles

Clip 13/18: Debrief Part 1

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Hillary Lewis and her educator colleagues engage in the first phase of a lesson study debrief protocol, in which the lead teacher and her co-planners share things that they observed and were significant. Her colleague facilitating the debrief asks the observing educators to share what “evidence they saw that students were able to classify triangles according to their sides and angles, and anything that you saw that helped students move their thinking from one position to changing their understanding and having a new position.” 

Hillary reflects on a few students whose thinking proved provocative and helped other students defend their thinking.

Teacher Commentary

Hillary Lewis

Me, personally, I find it fascinating to dig into, “Well, what did they understand?” and then, “Where did it fall apart? Where was the mix up?”

In this case with the triangles, it was usually that they understood one categorization but not a second one, that kind of thing. Or they overgeneralized what it meant to be acute, because every triangle has at least one acute angle, that kind of thing.