When 16-year-old John first entered high school four years ago, he worked very hard and always got very good grades. Besides doing well in his lesson, he was very active in sports. To get up very early every morning to practise running, he never took the school bus to school, he always ran there. He even won a silver medal in the 800-meter race at the school sports meet a year ago. As a reward, his parents brought him something that they had wanted him to have a long time -- a computer. Something began to change. He stopped getting up early and never ran to school. His interest in sports suddenly disappeared. Sometimes he got up so late that he would miss the school bus and thus miss school.

　　Soon his school began to suffer. One day in the middle of the night his mother saw light in Johns room. She went in and discovered the cause of Johns change. John had played computer games late into the middle of the night ever since he had his computer. This had bad effects on his study and he suffered from lack of sleep. This must be stopped. The next day she had a serious talk with John. Instead of taking away his computer, she told him he was old enough to learn to have some control over himself. John was happy he had such a wonderful mother and promised to correct himself.