Second Graders, Estimation 180, and a Clothesline

My second graders LOVE Estimation180 and we use it all the time. We recently did a unit on addition and subtraction with metric length. I thought the height estimation tasks would be perfect for my second graders, and they were! We started with the picture of Andrew Stadel and estimated his height in centimeters.

Mr. Stadel

We spent a lot of time discussing the importance of a “too low” and “too high” estimate and how these do not need to be outrageous numbers. We also talked about that our reasoning can not be, “I guessed” but must be mathematical. Most estimated he was 2 meters or 200 centimeters because he looked taller than me and meters were what they were most familiar with. Mr. Stadel ended up being 193 centimeters.

The next day, we estimated Mrs. Stadel’s height:

Mrs. Stadel

I had students do this one independently in their math journals.  I told students that I told Mr. Stadel on Twitter that we were doing his website and that he wanted to know how they did. This sparked concentration as they wanted me to take a picture of their work to send on Twitter. For Mrs. Stadel’s height, most students picked their too low as 160 cm, which was my height. They then picked 200 centimeters as too high since they knew she was shorter than Mr. Stadel (most didn’t remember 193, but could remember 200). I walked around with green and red rectangles cut from construction paper. I got the idea from Mr. Stadel’s blog, of which I am quite the stalker…in a good math way of course.

Sidebar: I’ve had a clothesline/string in my room for years that I have done to help with number sense and spatial reasoning. The way I have always used it with second and third graders is that when students come in the room in the morning, there is a number on their desk. At the beginning of the year, it is counting by ones starting at one and transitions to counting by ones starting at higher numbers, skip counting, using fractions, decimals, etc. The number sequence would stay the same all week. My string was always against a bulletin board, so my students used thumb tacks to tack their numbers to the string. At the end of the day, my late bus riders took the numbers down and redistributed across the desks. Students loved it, it was part of our routine for Mon-Thurs. On Fridays we completed a class graph (bar, Venn diagram, or line plot). I was used to a clothesline, but had never used it in an actual task until reading Mr. Stadel’s post.

Back on topic: As I walked around the room, I gave students a red card if I wanted them to write down their “extremes” of too low or too high. I gave them a green card if I wanted them to write their actual estimate. We then talked about the order of these on the empty clothesline. The red cards should be on the ends with the green cards in the middle if we estimated correctly. The red cards also shouldn’t be extremely far away from the green ones if we are picking numbers that are just TOO low and high. I, unfortunately, did not take pictures of this lesson…but I did the next day! This lesson sparked great conversation, not only about estimating and measurement, but number sense in how to design a number line that didn’t have a starting point or was counting by a specific number.

Day 3: We estimated the height of Mr. Stadel’s son:

Mr. Stadels son

We followed the same procedure from the previous day, except I took pictures of what happened. As you will see, some of their too highs and too lows could have been better, but for 7 year olds doing this for only the second time independently I was proud.


I am looking forward to doing many more tasks involving the clothesline than the way it’s always been done…although I love doing it my old way as well!


About Christy S

I am a math teacher that LOVES mathematics and wants to continually improve to make math make sense to elementary students.
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