## Barbie Bungee

Please don't read this and think I deserve credit for Barbie Bungee. This is a well-loved, widely used activity, and for good reason. Don't believe me? Use the #MTBoS search engine, key in Barbie Bungee, and watch the hits pile up. Fawn's done it. Dan's written about it. And, so have countless others.

As luck would have it, I caught Dan Meyer's "Full Stack Lessons" talk at CMC North just shortly before I was planning to use Barbie Bungee with my 7th graders.^{[3]}His talk spoke at length about this task as an example of how the same task can be engaging and valuable in one classroom but be drab and worthless in another. The presentation was great and pushed me to think about the types of actions and thinking my students do when they complete tasks in my classroom.

I've thought about this before, and I worry. I worry a lot about two things I deny my kids. I deny them with my too-carefully scaffolded and overly-planned lessons. I deny them opportunities to ask their own questions and to develop the method for which they will solve questions. I've fought this before (see: Fermi Estimation Problems) but a new school, a new text, new families, new students, a new coast, and more and more new stuff has made me feel like I've lost a bit of my mojo for building this into my classroom and my practice.

Dan's presentation was a wonderful reminder of the opportunity I had. The opportunity to "be less helpful" and to, therefore, help my students. So, I spent the drive home from CMC North percolating over how I would structure Barbie Bungee to de-scaffold it for my students' benefits. Here's the structure I landed on. I hope it is helpful to you as you consider implementing this or similar tasks:

- I arranged the students into groups of 4. Partners are my preference, but I worried about handling twice as many groups
- I purchased a unique doll for each group. This eliminated cross-copying of values and ideas since they had different heights and weights
- I broke the task into 3 distinct "drops". Where kids did the following for each one:
- Agreed on a number of rubber bands needed for their drop (2 x 45-minute classes)
- Dropped their doll and recorded the results in slow-mo (30 minutes or 2/3 of a class)
- Completed a reflection about what they did, why, if it worked, and what they wanted to do next time (15 minutes and homework)

**I provided MORE scaffolding at each drop**^{[4]}Yes, I know this sounds wrong- On the first drop, I said "figure out how many rubber bands you need."
- On the second drop, we brainstormed mathematical tools that might be helpful. Then I said, "figure out how many rubber bands you need."
- On the third drop, I had them complete a T-table, plot the points in Desmos, graph their own line of best fit, and then have Desmos calculate a linear regression, so they could, "figure out how many rubber bands" they needed"

This is not the normal progression I follow in my classroom. But, I think it is right for this task. There were so many good conversations; I can't possible recreate them all here. But, I do have one example that I think is illustrative of what I was going for.

We had a serious lack of meter sticks in the classroom, so students got inventive and began taping rulers together. I noticed that they were taping the rulers end-to-end which, frankly, makes lots of sense. Except....

Rulers leave a length on either end (presumably for manufacturing purposes) that isn't part of the 12" distance. But, my students ignored this gap. Did I point this out to them? Yes, but only after they were done with all of their measurements.

Why wait so long? Well, I wanted it to be too late to redo the measurements. So, instead of starting from scratch because of what their teacher told them, they had to adjust their model to deal with an error they discovered in their methodology. They had to figure out if their error made their measurements too long or too short. So much good thinking and conversation came out of this. Maybe more than any other part of the activity.

Too often, I get lulled into thinking that learning is this really linear and well-defined trajectory. My kids really learn the most when I remember that class can (and sometimes *should*) be messy. Their own ideas lead to natural teachable moments and errors where they are curious and engaged and passionate.

At a talk, I once quoted Lord Petyr Baelish who said, "Chaos isn’t a pit. Chaos is a ladder." Like all Westerosi men of lessor houses, I certainly need reminders of this wisdom. Perhaps this could even become my house words. I need to remember to welcome chaos into my classroom when it is to the benefit of my students.

**Propaganda Time: **Androids (yes, I guess iPhones too) can shoot HD slo-mo video. So, of course, I had to put a video together for my school:

**"Next Time"s**

Next time, I want to more explicitly connect the work in Barbie Bungee to other investigations. Specifically, the stacking cups investigation we had done previously. I mentioned this in a reflection question, but I want to spend more time on this. Perhaps even make it the a key part of my assessment.

Next time, I think I want to mix up the groups between each "drop." The thing I am most proud of in my classroom is that students regularly explain ideas to one another (SMP3). Mixing up groups will allow kids to say, "Oh, my group tried this and it ___________."

Next time, I need to build in a lesson on linear regression prior to this activity. The kids thought it was cool, but didn't really "get it"