In the lower elementary grades, kids might get their first exposure to pattern blocks. In fourth grade and above, you can explain that symmetry is the "exact correspondence of a shape on either side of a dividing line." Using pattern blocks, students can make a pattern on a piece of white paper with a center fold. Then they can perform the mirror test. Hold up the mirror at the dividing line of their pattern block arrangement. Determine if the image in the mirror is the same as what they see on the other side of the line.
Teachers can use a math Web site with animations and other graphics-based activities for upper elementary grades. On Mandy Barrow's Maths Zone, the user clicks on different shapes and figures to view the line of symmetry. On Tab 2, the user sorts a series of geometric shapes into three categories -- horizontal line of symmetry, vertical line of symmetry, or both.
Take the class through a Web quest with all information about symmetry and learning activities based on links from a single Web site. At Sherryle Mathis' site Symmetry All Around, students move from introductory activities, such as identifying symmetry in regular polygons and creating symmetrical snowflakes to designing their own quilt.
Some letters of the English alphabet have their own kind of symmetry. On the Web site of The Annenberg/CPB Math and Science Project, students view variations in symmetry through four alphabetic examples -- H, M, S, and B. For example, the letter M has a vertical line of symmetry but not a horizontal line of symmetry. That means you can fold it in half over the vertical line but not over the horizontal line when the letter M is upright.