Prove it!

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SWBAT identify key attributes for plane shapes. SWBAT create a set of rules that define what each shape is.

Big Idea

This is a great introduction to geometry in first grade or could be used as a Kinder lesson! Students use attributes to "prove" that they have a given shape.

Setting Up the Learning

5 minutes


You learned about shapes in Kindergarten. We are going to build on what you learned in K to help you think about shapes in more complex ways.

 Sing the Shapes Song. This is always a hit, even though it seems babyish!


Shapes are really important because different people use them every day for their jobs. Engineers use shapes when they are designing different things. Architects use shapes to help them design buildings.



Today, we will review the important attributes of triangles, circles, squares, rectangles, hexagons and rhombuses.  

Opening Discussion

15 minutes

Present Problem: I have a big bag of shapes I'm going to use to make Christmas decorations for my house. The problem is I don’t know what to call the shapes. You are going to teach me the names of the shapes and then prove it!


I’ll present  a chart with each shape name on it. Students place a picture of each shape on the chart (or in pocket chart). Then I’ll ask students to help me make rules for each shape. How do we know for sure that is the shape?


Before we discuss the actual shapes, we will define the terms “side” and “corner”.


Guiding Questions:

  • What shape is this?
  • How are you sure that is the shape?
  • What sentence could I write to prove that this is the shape?
  • How are you sure this is a rectangle, not a square?


Probing Questions: These questions get at students understanding of important shape attributes. The standard (1.G.A.1) asks students to think about whether or not an attribute that a shape has actually matters.

-Is this a triangle because it is yellow ?

-Is this a circle because it is big?

-What if I turn this shape on its side? Will it still be a triangle? How are you sure?

-What if I added another side to it? Would it still be a triangle? Why not?



Student Share

15 minutes

Students practice identifying shapes and listing key attributes for them in a group activity.

I’ll have students sit in little circles on the rug. They will each get 4 shape cards from an envelope. Then they will take turn laying the shape cards in one of the shape groups.


Sentence stem to scaffold this Common Core level discussion!

“This is a ___________. I know because ___________________”

Then the student can add it to the group of shapes.

 See this video of a group doing this activity!


After students finish, I'll show a picture/doc camera view on promethean board or have students stand around one group of objects and determine if the grouping is correct.

  • What shape name do you think this group used to describe these shapes? How are you sure?


See attached document for the shape cards I used! I printed them on different colored paper so students could see that the shape stays the same, even if it is on a different color.

Independent Practice

15 minutes

Students cut out pictures and sort them into groups, labeled with the shape name. Students write at least 1 attribute that the shape has, aligned to the CCSS focus on writing across the curriculum. 

Group A: Intervention

Students cut out and sort 2 pictures per category. Students may do this with a “reading partner” if needed. Students may need to be interviewed for writing portion.

Group B: Right on Track

Students cut out and sort 2 pictures per category. Students write a rule to go with each category.


See attached documents for Independent Practice!


5 minutes

Students share one shape category with a partner and explain how they knew what those shapes were.