How Long Is Yours?

I have been reading my mathematics textbook, “Elementary and Middle School Mathematics: Teaching Developments” sixth edition by J. Van De Walle, and I stumbled onto a statistic that made my jaw drop.

The textbook quoted a study (Kenny & Kouba, 1997) where “only 24 percent of fourth-grade students and 62 percent of eighth-grade students could give the correct measure of an object not aligned with the end of the ruler.” (Update: originally I typed that they "could not" give the correct measure. The stat is right now.)

Sixty-two percent of eighth graders could not measure the crayon above if the crayon sits in the middle of the ruler. That is because we teach mathematics incorrectly and we have for decades. We focus on learning the procedure and take no time to help children develop the concepts. In this case, we need to explore, not the hash marks on the ruler, but the space between them. In other words, what is it that a ruler actually does and means? Then we can teach the appropriate rules on using a ruler.

I would think boys would be especially interested in learning how to use a ruler properly. They do tend to like to measure thingy-dingys. Maybe that’s the problem. They want to see a thin 3-inch crayon as a fat 6-inch marker.

(In the interest of disclosure you should know this post is using secondary sourcing. I pulled the stats from my textbook and not the original study.)

Kenney, P.A., & Kouba, V.L. (1997). What do students know about measurement? In P.A. Kenney & E. Silver (Eds.), Results from the sixth mathematics assessment of the National Assessment of Educational Progress (pp. 141-163). Reston, VA: National Council of Teachers of Mathematics.