Living on the Edge

As we walked into the “other” middle school across town, one of the teachers teaching the lesson was running back in with a new package of rubber bands and a receipt. Apparently during a bungee test run the rubber bands they originally purchased were too tight – so he had to run out and get new smaller stretchier ones:

Big Ones

Big Ones

Little Ones

Little Ones

Barbie's ankle anchor

The original large rubber bands would be used as anchors for Barbie’s ankles.

Next we assembled what one teacher dubbed “pre-packaging” – but first we had to free the Barbies from their childproof packaging.

Prep 2

Each “package” was a large ziploc bag that included:

  • 1 Barbie with a rubber band anchor tied around her ankles
  • 9 rubber bands (size 19)
  • 4 rulers
  • 4 markers
Barbie Packages

Barbie Packages

Barbie Packages

Barbie Packages

And one extra mermaid

And one extra mermaid

We also realized that Barbie needed to have her arms above her head and her hair tied back to make it easier to see the height of the jump. Accuracy could prevent a broken arm or a fatality.

After our assembly of packaging we got down to the nitty gritty. What were our goals for the lesson and what did we want to look for during the lesson?


  • Math applications
  • Creating a scatter plot with a best fit (trend line) and writing an equation
  • Understanding and applying slope and y-intercept
  • How to use data to make a prediction
  • Team work
  • CCSS Math Practice 1: Make sense of problems and persevere in solving them
  • CCSS MP 3: Construct viable arguments and critique the reasoning of others
  • CCSS MP 4: Model with mathematics
  • CCSS MP 5: Use appropriate tools strategically

Look Fors: Each observing teacher would script the following while observing the lesson:

  • Team structure (participation and communication)
  • MP1
  • MP3
  • MP4
  • MP5
  • Pacing, timing, transitions

Each lesson started with the last 1.5 min of this video

Then we were into lesson #1. I was scripting MP3. Amazingly it all went very smoothly. With the students fully engaged in the lesson, the time (and Barbie) flew by – but no rubber bands did (to my amazement!) Unfortunately, most groups only got to complete their data and set up their graphs. So the homework became completing the graphs, line of best fit, and making a prediction for the 5 meter jump Barbie will take later in the week.

Lesson 1 Lesson 2 Lesson 3

Debrief Time:

We tweaked the data table and removed the column for averaging the 3 jumps. We also added a place for a prediction after the data was collected but before the graphs was complete. And then a space for a final prediction. We were hoping for more discussion, critical thinking, explaining. We also talked about what would happen if we didn’t tell the students to start with one rubber band and add one each jump. What if we gave them 9 rubber bands but no instruction on how to collect their data? What would happen then? In the interest of a 45 min class, we decided to keep the lesson as is – but if we teach it in our block days at the other school we could add this for a point of discussion/critical thinking.

MP 1 and MP 5 went well – no tweaking needed.

But MP 3? In general, the students were too polite. They accepted each other’s reasoning too easily. They let the “smart” kid lead without question. Do we need sentence starters to help the critiquing process? Do we need to teach higher order questioning skills? Or should we use the “mistake game“?


Starbuck’s, cookies and the Hulk are necessary for a good debrief

Lesson #2: The teacher also added this video: Again no abuse of rubber bands or Barbies, but lots more discussion, even some arguing. Several of the groups decided to find averages anyway “We’re geniuses!” one group proclaimed when the idea came to them. Adding that line about a second prediction helped facilitate MP 3. And some groups wanted to jump to the scatter plot before making the prediction. Really? Isn’t graphing just more work? Apparently not. Leaving the graph axes blank prompted quite a  bit of discussion as well. What scale should they use, how should they be labeled and why? This class got a little bit farther on the worksheet.

Lesson 5 Lesson 4 Lesson 6

Follow up? Once the students complete their predictions they will explain how and why they made them to the class. Then Barbie will jump from 5 m and we are looking forward to video and/or vine to see which group  will give Barbie the best ride. At the other middle school, we will also attempt the Barbie Bungee. Anyone have some Barbies you’d like to donate? Email me

Lesson Study #3? Yes! We all agree this is valuable so let’s do one on quadratics! This time our high school cohort can teach it since they’ve taught quadratics before.

Thanks to our team of 8 for participating and making this an awesome day!

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