Show the children a two-dimensional circle. Describe its properties by saying, "This is a geometric shape called a circle. We know it's a circle because its edges are curved." Contrast it with a square or triangle if the children have already been introduced to those shapes. Say, "It is different from a square because it doesn't have any flat sides or corners." Ask the children to point out any circles they see in the classroom. If someone points out a ball, say, "Yes, that is a circle, but we call that a three-dimensional shape."
Teach the children a song related to shapes to help them remember and understand the concept. Create movements to go with the song, perhaps drawing the shapes in the air with a finger or making the shapes with hands. A song familiar to most preschoolers is "The Wheels on the Bus Go Round and Round." Other appropriate songs include "Circles Go 'Round and 'Round," by Jennifer Fixman, and "The Circle and Square Song," by Rita Gold. Use the songs as a warm-up for future circle lessons.
Provide small groups of students with old magazines and safety scissors. Ask the students to find and cut out as many circles as they can. Give each student a piece of construction paper in the shape of a circle to glue their circles in a collage. Remind the students of the properties of a circle and encourage them to ask if they are unsure whether they have found a circle. Allow them to present their collages when completed.
Give each child a piece of paper with drawings of two or three circles in various sizes. Ask the students to trace each circle and then color it in. As they trace, ask questions like, "Does a circle have any sides? Corners?" Talk about how the hand makes one smooth, curved line when drawing a circle. Show the students how to draw a freehand circle on the back of the paper and allow them to practice several of their own.
Challenge the students to think of the circles they see every day. Make a list on large paper to display and add to later. Encourage the students to think of everyday items, such as dinner plates, clocks, traffic signs or even the sun and the full moon. Ask them to pay attention when they go home to see how many circles they can find in their own home or neighborhood.