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In this month’s letter, I invite you to step back into different classrooms to observe, with intention and calm, how children think when they solve WODBs.
So, what are WODBs?
A WODB (short for Which One Doesn’t Belong) is a very interesting math activity that is easy to incorporate in early childhood.
The routine involves showing students four items arranged in a 2 × 2 grid. First, we analyze the characteristics or attributes to identify what they have in common. Next, students determine which item should not belong because it lacks a property shared by the other three or possesses a unique property that the others do not have.
The most intriguing aspect is that any item can be the one that doesn’t belong. Each item shares certain characteristics with the others but is also different in some way. The key is for students to explain and justify the choice, as there is no single correct answer.
Why is it interesting in early childhood?
These activities promote critical thinking from an early age and allow us to observe how children justify their choices, listen to others, and connect with mathematical processes such as Reasoning and Proof, as well as Communication and Representation.
Moreover, they don’t require special materials: they can be facilitated at any time of day, either as a thinking routine or as a warm-up before a math session. These activities can be easily adjusted to match the developmental level of the group.
Next, we’ll look at examples of children doing WODBs for the first time.
In this video, we see children solving a WODB using four pictures of birthday cakes. The teacher begins by asking the question Which One Doesn’t Belong? and gives children time to look closely at the pictures, one at a time. As a group, they first identify what the pictures have in common—in this case, that they all depict birthday cakes.
As the conversation continues, children suggest different criteria for determining which item could be the one that doesn’t belong. Some focus on size (the biggest or the smallest), others on shape, color, the presence of candles, or the shape of the candles, as well as the presence of numbers, written words, or even the fact that one of the cakes is sliced open. Each new contribution broadens the group’s thinking and illustrates that there is no single correct way to analyze the situation.
The teacher supports this process by capturing the children’s ideas, restating and connecting them, and helping them use more precise language to justify their reasoning. She refrains from validating one answer over another, instead valuing a variety of arguments and making it clear that all of them can be valid if they are well explained.
This example clearly shows how WODBs encourage children to observe attentively, compare, explain their reasoning, and listen to others. Here, math becomes a space for conversation and collaborative thinking, where each new idea contributes to a deeper understanding of the situation.
This activity is a small example of the learning opportunities you can offer in the classroom through brief activities like WODBs. In the video, you saw one example, and for teachers who have access to the Classroom Manager, you’ll find many more WODBs under Quick Games in the Classroom Life section:
