I was enlightened to this resource's existence a little over a year ago via the magic of the #MTBoS. I have used it with students and teachers, both of whom love it as much as I do.
The biggest thing I have learned is that the prompt, "Which one doesn't belong?" was leading my students/participants to think there was one right answer, which I didn't want. Rather, I wanted to see what they knew about the numbers/shapes/graphs we were analyzing, and their relationships to each other.
So, the prompt shifted to "Find a reason why each one doesn't belong," and the reasoning and open communication followed; students began making observations and noticing things that I didn't even think of, because they were trying to find reasons for all of the quadrants rather than focusing on one "correct" answer.
The sample above is my favorite to use as a first experience with WODB for both teachers and middle school students. You can see the bullet points which are reasons 6th grade students shared for each number. My favorite is the second reason for 9: "only number whose digits don't add to 7." Awesome.
Beyond fun, this allows teachers to assess students' prior knowledge of numbers - vocabulary like perfect square, prime number, factor, multiple, and digit all came up naturally in this class.
One of the teachers I work with this year is developing many of his own with graphs and equations for an Algebra I class, and we are seeing students make sense of the features of both as well as the relationships among representations. We were inspired by images like these from the site:
I am excited about this resource, and hope we can all continue to contribute ideas to grow it more and more. I will leave you with some of my favorite shapes sets:
