If the teacher is teaching children about polygons, prior to the lesson she may ask them to list all the real-life objects they can think of that are polygons, such as triangles, pentagons or octagons. Possible answers might be a stop sign, the Pentagon in Washington or a slice of pizza.
Divide students into small groups and have each one come up with a math problem whose solution is the number 2. To make the exercise more interesting, each team must come up with a different type of problem -- so if the first team's problem is 6-4=2, then the second team cannot use a subtraction problem. The new team must switch to an addition, division or multiplication problem whose answer is 2.
Just before lunch or the end of class, the teacher passes out small "tickets" to each student. Before they can leave, students must write down two more questions about the math lesson they just covered, or two more things they would like to learn, as an encouragement to keep thinking about the subject.
The teacher may have children form small groups and task them to describe, or summarize what they just learned in their own words. Alternatively, she may tell them to explain the most important parts of the lesson to each other, or to imagine how they might apply the lesson to real life, such as using fractions in recipes.