Bring a square handkerchief in the classroom. Fold it horizontally, vertically and diagonally to show how a shapes' one half can fit perfectly over the other. Draw a line after every fold and show the handkerchief with all its symmetry axes to students.
Draw a series of geometric shapes on the board, such as an equilateral and isosceles triangle, a rectangle and a rhombus. Ask children to copy these shapes on their notebook using their rulers, cut them out with their scissors and practice folding them. Instruct them to draw the symmetry line every time the folded parts fit perfectly.
Explain why line symmetry is also called reflection or mirror symmetry (because if you stood a mirror on the line and looked from either side you would see the full shape). Prepare a worksheet with a number of shapes and ask children to draw a tick next to those they believe are symmetric and an "X" to those students think are not symmetric. Go over to each student with a small mirror, place it on the symmetry line and allow children to evaluate their own answers.
Chat with students about objects in the real world that are symmetric (not necessarily perfectly). Examples are an open notebook, the human body, a car seen from the front, a butterfly with open wings and a solid-color shirt. Give one or two examples and allow children to do the rest of the talking.
Prepare a worksheet with all letters of the Latin alphabet, copy it and distribute it to children. Give them 6 to 10 minutes to compete against each other and spot as many symmetry lines as they can. The student with the most correct lines is the winner.
Ask students to make their own symmetrical shapes for homework. Allow them to draw anything they want (real or imaginary objects), as long as they feature at least one symmetry line.