8 ways to make your Classroom Activities more CBL-ish

Tower Building Challenge 

Tower Building Challenge in 8th Science
Tower Building Challenge in 8th Science

One of the learning experiences that my 8th grade Science students remember each year is a tower building challenge. This hands-on activity supports many of the concepts I am responsible for teaching in my 8th grade Science curriculum, but even more importantly it is a great opportunity to put Challenge Based Learning into practice…even if in small ways. So while perhaps some would say this isn’t 100% CBL, I believe that small shifts in doing things CBL-ish have great value as well!

#1 Keep the challenge open-ended, not prescriptive.

Big Idea: Structural Engineering 

Essential Question: How can a structural design score the highest strength-to-weight ratio?

Challenge: Build the tallest, strongest tower possible.

While other learning activities might give students step-by-step instructions or very specific parameters, simply phrasing the task as an open-ended challenge adds excitement and intrigue from the start. 

Although I give Tower specifications, there are still a lot of opportunities for inquiry and innovation in this challenge. In Challenge Based Learning, some parameters can encourage creativity.

Tower Specifications 

  • Tower Height must be a minimum height of 30 cm and maximum 70 cm.
  • The base of the tower must span a hole a 16cm X 16cm (from any combinations of sides.) A little bigger is better. 
  • Top opening in the tower must be at least 5cm X 5cm (to fit load chain.)

Towers vary in technique, design, and appearance. Students can see how original ideas helped (or hurt) their team’s solution design. Simply asking students to successfully follow the steps of a lab would not have the same impact as a more open-ended challenge does. 

#2 Encourage collaborative work.

The typical junior high group task involves a divide and conquer approach— dividing up the questions or vocabulary words to minimize individual work load. The tower building challenge offers a chance for higher level collaboration- each learner contributing ideas, research, and hands-on work towards a shared purpose and common goal.  Generally I let my 8th graders choose their own collaborative groups for the Tower Building Challenge, but throughout the year there are other activities where I intentionally make the groups. Using CBL in differing ways throughout the school year builds up students’ collaborative skillset.

#3 Provide a tool to document the process throughout.

For this challenge I use a Numbers document (attached at end of post) so that my students can track their daily progress using data, images, video, and voice reflections. While Numbers is traditionally a spreadsheet tool, it also allows for drawings, media, and whiteboard space organized into tabs(sheets). This is a perfect scaffold for my 8th graders to have some structure, but also allow for open-ended creation within that space. In CBL it is more about process than product, so student documentation of every step along the way is an important cornerstone. 


Screenshot of Numbers template for Tower Building Challenge
Screenshot of Numbers template for Tower Building Challenge

#4 Allow ample time for investigation.

Encouraging students to generate their own research questions is the first step to making our classroom learning more challenge-based. We start with surface level questions and defining all key terms. What does strength-to-weight ratio mean? What is buckling, deflection, lateral force? Then I have students in their teams generate their own guiding questions… the things they will need to know in order to create a solution design. Taking time for students to generate their own questions about the challenge, ask others for professional insight, and research structural designs in other spaces allows them to be more self-directed learners. What they discover through their investigations is applied to their prototypes and plans, and it makes a world of difference to not let learners quickly rush to the first solution they come up with. CBL allows us to “stay in the question longer” and this is important for deeper learning.

#5 Connect with real-world experts.

One of the easiest ways to make your classroom lesson more CBL-ish is to connect with real human beings outside of the classroom. In my Tower Building Challenge, my students spoke with their relatives with engineering backgrounds, farmers who created makeshift solutions for similar daily tasks, and even local community members with insight on how these concepts transfer to the real-world. Giving students a reason to ask questions and learn from other humans is one of the best gifts of CBL, and no matter the size of the project, I see the benefit in building in these expectations for my 8th graders. 

#6 Build in time for reflection.

Like allowing time for questioning, I have also learned the importance of building in intentional reflection at key moments in a classroom project or challenge. Sometimes I give students sentence starters and tell them to use PhotoBooth on their Mac or the rear-facing camera on their iPad/iPhone and just finish the narrative. Sometime an audio recording right within their Numbers document is enough. Other times a written reflection in our class LMS that others can read is the preferred reflection activity. No matter the kind of reflection, this metacognitive practice not only helps students focus on their own personal learning journey, but also gives me insight into additional support students might need. In addition, student reflections offer a more authentic way to assess learning as well. 

“Today I was happy about…”

“One thing that didn’t work the way we expected was…”

“I wish we knew more about…”

#7 Incorporate meaningful use of tech.

Students use their iPad camera to capture their tower in its various stages of development and of course slow-mo video at the point of its destruction! They use Apple Pencil to sketch out diagrams, the Measure app for quick measurements with Augmented Reality, audio and video recordings for interviews and reflections. Having choice in how students create their design prototypes is extremely beneficial. Some groups would rather sketch on paper and then capture photos of their designs. Others would rather using Keynote shapes and drawings to design digitally from the start. iPad and Mac become “just in time” tools that support the entire process toward a solution, instead of an “add-on” technology expectation at the end of a lesson. This models what they will experience in their future careers as well. 

#8 Celebrate failure as well as success!

At the time of judgement, each student group tests out their balsa wood tower by gradually adding more and more weight until it collapses. Students are armed with their iPhone or an iPad, ready to capture the moment of destruction in slow mo video. After calculating the strength-to-weight ratio of each tower, the winning designs were applauded and year-to-year leader boards are updated. But I see this final culmination of the tower building challenge as such an argument for CBL in education.  Whether a winner or not, the slow mo videos are by far the highlight of the entire experience! Where else can we celebrate our failures in such a positive and enjoyable way? Even the winning towers have to collapse in order to get scored, and the joy and delight that students have for each other in this moment is palpable. Through Challenge Based Learning, students are empowered to work together to come up with original thinking backed through research and share their triumphs (and failures) with the rest of their learning community. It is science class magic. 

For more ideas about using Challenge Based Learning in middle school science, be sure to check out this article:


For more on the Balsa Tower activity, view this resource from TeachEngineering: 



4 replies

January 12, 2024

I like how you used a Numbers document so that my students can track their daily progress. I think Numbers is such a great and underused app.

January 12, 2024

This weaves CBL so nicely and easily into curricular content. Love the approach! It gives me a clear picture of how any content area might use this approach. I’m bookmarking this page!

January 12, 2024

This is awesome Kevin! Thank you!

January 12, 2024

This particular lesson you outlined makes me think of the show "Lego Masters." Could be a fun pop culture connection to bring into the classroom when students are working on this project! I love how you described celebrating failure as part of the learning process throughout this CBL project and especially in the final weight-testing challenge. I think it is so important for us to demonstrate to students that failure is a natural and important part of the learning process. It helps our students be more willing to take risks in their learning and try new things.

Thanks for sharing, Kevin!

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