Fourth-grade textbooks carry solid information about angles, including congruent ones. Yet students' own bodies can also help them learn about the concept. A teacher should plan an outing to an open field or court with enough space for students to line up facing her. Once positioned, she can call for students to turn their bodies according to specified angles. For example, calling "left 90 degrees" means that students should make a quarter-turn to the left. A teacher can shout "congruent pairs" for the children to form congruent angles in groups of two.
The concept of congruence can challenge some fourth-graders. To make it simpler, teachers should introduce it as meaning "same size, same shape." This idea can lead to easy activities to reinforce the concept. As an example, a teacher could bring a bag of clean but mismatched socks to class. She should invite the students to pair the socks according to congruence: the socks that go together. The same experience can be had with Lego's or other children's blocks.
Kites provide children an excuse for outdoor play, as well as an easy introduction to congruent angles. The standard kite shape features two pairs of congruent sides adjacent to one another, producing one pair of congruent angles. A teacher should invite students to look at and feel the kite as an example of congruent angles in the real world. After giving them a clear definition of congruent angles, the kids should fly the kites to see them at work.
Corny old movies are hardly reliable entertainment for fourth graders' short attention spans. Yet quality educational films, when shown in small doses, can prove effective. Teachers can consider the oeuvre of Bruce and Katherine Cornell, well regarded for their series of animated films about geometry. Their 1977 piece entitled "Congruent Angles" marries old-fashioned geometric shapes with a simple script and a jazz score. Lasting only seven minutes, students can quickly watch the film before discussing congruent angles as a class.