Introducing Shapes in Preschool: Diamonds and Triangles

By Pam Cannon

Young children love to experiment with shapes and patterns. They can learn to tessellate, make sponge prints, look for shapes in the environment. What fun to make an alliterative story with Trevor Triangle or Desmond Diamond, or create shaped glasses to wear


The formal objectives of teaching preschoolers shapes - diamond, triangle - are as follows: Diamond and Triangles 

Students will discover that shapes are everywhere.

Students will identify triangles and diamonds by their characteristics.

Students will learn how to tessellate.

Getting Started

Gather students together and share a book about shapes. e.g The Greedy Triangle by Marilyn Burns. (The author offers suggestions The Greedy Triangle by Marilyn Burns for activities in the back of this book), The Secret Birthday Message by Eric Carle, Shape Space by Cathy Falwell

When teaching preschoolers shapes like diamonds and triangles, explain that you are going to be looking for two different shapes. (You may wish to look at diamonds one day, and then triangles the next day)

Diamond Day

  • Have available a sweater or Argyle socks so that you can show students the diamond patterns in this clothing. Do any of the students have diamond shapes in their outfits?
  • Ask students - What is a baseball "field" called? (baseball diamond)
  • Go for a walk around school and look for diamond shapes on the floor, on walls, on carpets - if your school has a baseball diamond go out and walk the bases.

Triangle Day

  • Have available triangular objects such as wire coathangers, or triangles from the percussion instruments. Go for a walk around the classroom and find triangles on the floor, or on the walls or tiles.
  • Draw a triangle on a chart or on the chalkboard, and then up against it, draw its twin "upsidedown", and then another right side up and so on. Show the students that there are no spaces between the shapes. Then tell them that they are going to know a most marvellous word that maybe even their parents will not know! TESSELLATE. Young children will love to be able to say this word and tell what it means. Tell them that they could make a picture of "Tessellating Triangles" when they go to their activity centers.

Diamond Day Activities

  • In the gym, invite groups of 4 students to lie on the floor in a diamond shape.
  • Provide diamond shape paper and ask each child to print their name - one letter on each shape. Then paste the diamonds onto large sheets of colored paper with the heading My Diamond Name.
  • Provide different size diamond shapes and invite the students to make pictures of characters with them e.g. Desmond Diamond, Deirdre Diamond. Do they have diamond shaped hands and feet? For more able student,s they could make up a story using diamond shapes e.g. Desmond Diamond lived on a baseball diamond and only ate diamond shaped cereal.
  • Students could use drinking straws to make diamond shapes and glue them onto paper. Encourage them to use different lengths but emphasize that they must have two the same length, and then another two the same length. This will show clearly the characteristics of a diamond shape.
  • Provide students with three different sizes of diamond shapes, and ask them to glue the biggest one on to their paper, then the middle sized one on top of the first, and the smallest on the very top.
  • Look at crackers and cereal squares such as mini Shreddies and show students how they can be turned around to make diamond shaped food. You could use some square shape preschool activities, to help with this too.

Triangle Day Activities

  • Teaching preschoolers shapes, wouldn't be complete if we didn't look at the triangle.
  • Together with the students look at triangles and discuss how many sides and corners a triangle has. Make a list of "tri" words and talk about the number involved.e.g. tricycle, tripod, triplets, trillion, trilogy.
  • In the gym, arrange groups of three students into triangles. Have students stand and put their hands on their hips. What is the shape made by their arms? How do they know it is a triangle (3 sides).
  • Provide many different sizes of triangles, and ask students to make a picture of a triangular character. Give the character a name e.g. Trina Triangle who lives in a tent and only eats triangular cheese.
  • Make triangular glasses to wear. Cut out triangle shape frames and add pipe cleaners as the ear pieces.
  • Remind students about tessellating triangles and encourage them to make up their own pictures.
  • Have students sit in a circle. Ask them to use their fingers. How many fingers are needed to show the shape of a triangle? Ask them to move one or two fingers to show how you can change the shape of the triangle. Ask them to make a triangle with their fingers that has all its sides about the same length.


When teaching preschoolers shapes like triangles and diamonds, informal assessment and evaluation will be mainly by observing the students when involved in their activities. Checklists may be used to monitor progress: Does the student recognize a diamond and a triangle shape? Does the student know the basic characteristics of each shape? Does the student understand the word tessellate?

Wrapping It Up

These preschool teaching activities for diamonds and triangles could be adapted to use with other shapes. Young children particularly enjoy making shapes with their bodies, and using their imaginations in creating shape characters.

It all adds up to a satisfying enjoyable day.

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