Although my students understood the concept of area and could accurately work out the answer to simple problems, I had observed them using a variety of approaches to finding the area of a square, rectangle or shape made up of their combination. Also, I wanted each student to become aware of the variety of approaches available amongst their peers so as to adopt the more efficient strategies that made sense to them. So it was time to design a formative assessment.
I gave each small group one problem at a time to solve. As each group explained to the whole class how they solved their problem, I wrote their strategy next to the given problem. We used two types of problems: shapes on 1cm squared graphing paper and similar shapes on blank paper. Students were free to collect and use tools as they needed such as rulers or more graph paper.
As students listened to their peers, there were those lovely penny-dropping moments. When finished, we discovered that we were ALL accurate but not as quick. We agreed on a simple key to evaluate each strategy by using "energy efficiency stars" like they do on electrical appliances.
Students were not only able to learn from one another, but they now have an anchor chart to choose, try or remember efficient strategies when finding the area of these shapes.