Why not start with standard units (like inches) when measuring length? Why not give young mathematicians rulers and teach them how to use it?
Here are just a few important reasons to begin with nonstandard units:
Nonstandard units are concrete.
It is essential to begin measuring with nonstandard units because they are a more concrete representation of measurement. Starting with nonstandard units emphasizes the concepts of measurement over the process of measurement. (See Conceptual Learning for more.)Nonstandard units motivate us to attend to precision.
Young mathematicians often get distracted by tools that have measurements that are too precise (like centimeters on a standard ruler). It’s better for them to have access to tools that match their level of attention to precision.
An important skill in measurement is choosing the appropriate unit; a diverse array of units to choose from helps hone that skill. Furthermore, when we use a variety of units, we need to state the unit of measure we’re using. This gives clarity when we communicate our findings to others.
Nonstandard units are readily available.
Whether in the classroom or at home, it is far more likely that students will have access to nonstandard tools for measuring (paperclips, popsicle sticks, clothespins, corks, beads, toilet paper tubes…you name it!) than standard tools like rulers, tape measures, or even connecting cubes.Nonstandard units reflect the real world.
So much of understanding measurement requires synthesis of real-world experience. Being able to compare, estimate, or choose the best unit of measurement depends on students’ hands-on experience with materials that relate to their daily lives.
Introducing Standard Units
Standard units of measurement like inches, centimeters, pounds, grams, or minutes have their place in the classroom, of course! The point here is that we introduce the concept of measurement using nonstandard units, and then students apply their conceptual knowledge using standard units. The below activity is an excellent transition from nonstandard to standard measurements for length.
Activity: Make a Ruler!
(Adapted from Teaching Student-Centered Mathematics: Grades K-3 by John Van de Walle and Lou Ann Lovin.)
For this activity, each student will need one long strip of plain paper or cardstock (sentence strips work, too!) and a dozen one-inch paper squares in two different colors, and some glue.
(Tip: purchase pre-cut mosaic paper tiles or use the trusty die cut machine at your school.)
Additional Resources
“Which Holds More?” Watch this video of from the Erikson Institute Early Math Collaborative to see two examples of open-ended exploration and comparison of capacity.