Another exploration we did was an "unusual units" study. The kids used pennies, paperclips, unifix cubes, and parallelograms to measure their journal, pencil, and table. I provided all the unusual measurement tools, making sure to include several different sizes of paperclips, and DID NOT give students directions on how to iterate units or which size units to use.
The children took their time as my only directions were to "measure very carefully and record all your data." Once the students had collected all their measurements, we transferred our numbers to class charts. This made the comparison easier.
As we discussed why some numbers were different, students came to their own conclusions about the importance of using the same size unit to measure with. They began to understand that it was also important to know how to iterate the units. Students guessed that the smaller numbers for parallelograms were from students that may have placed their parallelograms side by side rather than tip to tip. The kids realized that the pencil measurements were different because our pencils were all different sizes. I was able to call students up to demonstrate how they measured. We used different size paperclips to demonstrate that using big/small clips would change our number.