Have students stand with their feet shoulder width apart. Instruct them to squat down (as though they are pretending to sit down a chair), being sure to keep their stomach muscles tight and their backs straight to prevent injury. Using their arms for counter-balance, they can reach out. Tell them to slowly squat down until their knees are bent to 90 degrees, and knees do not go past their toes, hold for a count of 3 seconds and slowly stand back up. Do sets of 8-10 repetitions. You could encourage the students to also incorporate doing squats during a TV commercial, or doing a set of 10 here and there throughout the day.