During the day we work and play, and at night we sleep. Our bodies rest while we sleep. In the morning we are ready to work and play again. When we are asleep, our bodies grow most. Too little sleep will make us tired. Tired children need sleep.

    We can get better at our lessons after having plenty of rest. Boys and girls of eight or nine years old need ten hours of sleep every night. Our bodies need lots of air when we sleep. If we do not get enough fresh air we'll feel tired when we wake up. While in bed, we must not cover our heads. If we do, our lungs(肺) will not get enough fresh air. If we open our windows at night, we can have plenty of fresh air. Cool air is good for us. Boys and girls who want to be strong must get lots of sleep.