Students became familiar with principles of linear measure through a series of activities: measuring objects with non-conventional units, measuring their own height and comparing it to a classmate's, and small group and whole group discussion justifying rules they decided on for measurement.
During these lessons, students struggle with, but begin to understand, important measurement principles. It is important to provide children with further opportunities to learn about measure.
When measuring objects using non-conventional units, students encountered measurement issues such as zero point, gaps between units, and fractional units. Most students demonstrated and explained their understanding while working individually in small groups. This format allowed the teacher to highlight differences in children's thinking and to prepare situations that challenged students to correct the teacher's measuring "errors."
When measuring their own heights and comparing them, students struggled with how to measure lengths longer than a yardstick, often not realizing that the 36 th inch should count. (The rulers did not include a "36" label.) The children were not consistent when comparing the lengths of two strips-if they repeated the measurement, they often got a different answer. This was partly due to the long lengths being measured; the paper and rulers slid around, leading to inaccurate measurements. When they subtracted the shorter from the longer length they did not get the same answer as when they measured the difference between the two strips. They were not bothered by this discrepancy. Only one pair of students drew a picture of the situation and their solution. This diagram proved helpful in showing the class their solution. It was clearer than other students' descriptions of their strategy.
