I've been having my students support their answers with a "because" in reading for awhile now, but last week during math I realized I needed to do the same thing. As my 2nd graders were making models to represent repeated addition and multiplication, I started asking "What's your why?" when they showed what they created. Then, when my 3rd graders were rounding and estimating using a number line, I asked them the same thing.
Wow, the critical thinking and problem solving went through the roof! Some kids realized their answer wasn't correct when they couldn't tell me their why. Some kids had the correct answer, but couldn't tell me their why. It was such a powerful moment and I saw amazing learning happening!
I created this poster to keep up in the room as a reminder to myself and my students, know your why!