To introduce ways to record and display changes in plant height over time. To provide ways for students to calculate amounts of growth.

To create a record of plant size over time, the teachers made and labeled color-coded paper strips that showed the height of the plant each day. These strips were displayed in two ways. One display showed plant strips mounted along a timeline. The other displays showed the plant strips mounted on separate sheets to show change (in height) over time for each plant. [examples of displays] Copies of the labeled strips were also available to students for some tasks.

These paper strips were used several ways during the lessons. First, since there were only a few bulbs available to study, the students observed but did not handle the plants as the teacher made the strips. More importantly, since the children had not learned about linear measurement prior to this growth unit, the paper strips provided a record of growth, and an opportunity to invite students to determine how much the plants had grown and overall patterns of growth. To address questions about plant growth, the class completed a mathematics unit on linear measure .

On each measurement day of this unit (usually M, W and F), teachers cut and labeled paper strips corresponding to the height of each plant on that day. The strips were color-coded for each plant. These strips were displayed in several ways. One display showed all of the plant strips mounted on a time line. The other displays showed the strips for each plant mounted separately. These displays were used most extensively in instruction. Duplicate unmounted labeled strips were available for students to use in measuring tasks.

The paper strip displays allowed children to quantify plant size and growth and make comparisons between plants. Students readily noticed which plants were taller than others, supporting their ideas by referring to longer vs. shorter strips. The first step in quantifying growth came in a whole class discussion, when a student demonstrated that the difference in lengths between successive strips was larger for one pair of strips than for the other. She indicated this meant that the plant grew more.

Early student work with the paper strips revealed that the first graders did not understand measurement and had very little, if any, experience with it. One group of students attempted to measure a paper strip with a ruler. They reported that the strip was 15 or "about 9," and were confused by the discrepancy. (The actual length was 9 6/16 inches.) They had counted each sixteenth of an inch and added that to the nine inches read off the ruler. The teacher designed a set of lessons in measurement, which students worked on along with the lessons on growth. Growing understanding of measurement supported understanding of growth.

While trying to measure paper strips, many students used pencils as measuring tools. This activity highlighted principles of measure such as identical units, fractional units and conventional units.

To illustrate how much plants had grown, most students mounted two strips next to each other, aligned at one end. Then they used small units (1") appropriately to measure the difference. Many students demonstrated that they were attending to precision of measure as they reported the growth, for example, as "about 8 inches" or included a fraction (one half) of an inch when necessary.