In October of 2012, Andrew Stadel, a middle school math teacher, created a website called Estimation 180, **with the goal of helping his students improve their number sense**. Andrew considers estimating key to developing number sense and reason (we are inclined to agree). He teaches Pre-algebra, Algebra and Geometry, so his estimation challenges are not limited to a specific grade level.

Every day, Andrew gives his students **an estimation challenge** around a theme. He reveals a picture of an object, and students make an estimate about the object’s height, weight, or other measurement. Each chooses a number that is too high, one that is too low, and finally their estimate, allowing ALL students entry into the challenge. In addition, he asks his students for their reasoning, a great way to explicitly teach – and for students to engage in – Math Practice #3: *Construct viable arguments and critique the reasoning of other*s. There is potential for some great math talk here.

Estimation Challenge – Day 1

He’s also created a worksheet for students to keep track of their estimates, their reasoning, and their error percentage. It is a great way for students to track their own progress (a research-based strategy with a **high** effect size).

As **an engaging extension**, students and classes can submit their estimates right on the webpage, compare them to participants outside of their classroom, and see the reasoning behind others’ estimates.

Estimation Challenge – Day 53

Andrew has recently added a tab with lessons ranging from 4^{th} – 8^{th} grade that are focused on a particular **Common Core Standard**. His infamous File Cabinet task (picture below) is among those lessons he is sharing. A fan of 3-act tasks, Andrew cleaned up many of those found in his original 3-act catalogue, tagged them with Common Core Standards, and now includes handouts to go with the lessons.

Act 1 of the File Cabinet Task

When we think of someone who **walks the walk** with regard to what it means to teach with the math practices in mind, Andrew Stadel is one who comes to mind. He incorporates student collaboration and problem-solving into his lessons while balancing the need for individual think-time and accountability.

You’ll find Estimation 180, as well as a link to Andrew’s blog, Divisible by 3 on our Math Symbaloo. The math half of us would **LOVE **to model this in your classroom.

We encourage your comments.

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aweekoraweekendPassed this right on to Jeff. Looks like great stuff!