Co-Teaching Lesson: Properties of Triangles (Shari/Paula)

This is the 3-part lesson we observed during our co-teaching session with Shari and Paula at Lord Roberts on Thursday.

Materials from the co-teaching session can be found through these links:
Three-Part lesson plan
KWC Chart
Assessment for Learning template


Prior to the lesson:
Students in Shari's class just began their Geometry unit.  They had one lesson around the properties of triangles.  This was the second lesson in their unit so it's more a diagnostic task.


The class had a lot of prior experiences with the problem solving process and the KWC chart:

The KWC chart and how it fits into the problem solving process.

The steps in the problem solving process.

Success criteria for the problem solving and communicating process.

Part 1:  Activation of Prior Knowledge

The goal of this part of the lesson was to make sure students understood:

- what a relay race look like
- the difference between a rectangular and square relay course
- what a triangular course might look like


After students demonstrated what a relay course might look like, Paula asked students to share what they knew about triangles.  She recorded their ideas on chart paper so they could refer to it while solving the problem, which they did!

Part 2: Working on It
Shari introduced the problem to the class. 

After the class read over the problem together, she recorded their ideas on the KWC chart.

When this was done, she asked: What do you need to do to be successful in this task?  


She recorded their ideas on chart paper, with little editing.

Shari and the class have co-constructed success criteria for the problem solving process prior to this lesson.  This was their first attempt at co-constructing the success criteria for a specific problem.

Part 3: Reflecting and Connecting

Many groups struggled with this problem.  Shari saw this as a positive since it illuminated a lot of student misconceptions, which she can address during the unit.

The groups that were chosen to share their work during the math congress all brought out a key point Shari wanted to make to the group.

This group generated a lot of possible triangles that met the conditions for the lengths but ignored the necessary angles. Once they realized that the triangles needed to meet all the conditions, they confessed that the problem became harder.

This group had an accurate solution.  However, they began with the side lengths as well.  They could not articulate the process they went through to make sure the angles were correct as well.

This group's work was incomplete but contributed to the big idea that constructing the angles of the triangle first, then the side length is a preferred process.  

Explicit Teaching

This group did not share during the math congress but was reflective of the process many groups went through.  Shari used it as example to illustrate how starting with the side lengths was easy but finding the right angles was more difficult.

Teacher Reflection

The entire class demonstrated perseverance throughout this problem.  This was something Shari appreciated about her class and she referred to this during her debriefing with the group.