People always say to students that their main duty is to study and they should not spend time on other things except for study. However, most boys are born to love exercise, especially ball exercises.

People always say to students that their main duty is to study and they should not spend time on other things except for study. However, most boys are born to love exercise, especially ball exercises. Thus, they are always blamed to spend time on playing balls, instead of spending all time on study. In my opinion, the idea is wrong. Proper exercise is good for study. Exercise can help students relax their mind and body. After a long time study, they need it very much. After relaxing, they can have a good state to study, which will improve their study efficiency. Besides, students always can sleep better after exercise. If they sleep well, they can have more energy on study. It promotes study. But spending too much time on exercise may have bad influence on study. 
人们总是对学生们说他们的主要任务是学习，除了学习不应该把时间用在别的地方。然而，大部分男孩子都是天生爱运动，尤其是球类运动。因此，他们经常会被责备把时间花在打球上而不是把所有时间都放在学习上。在我看来，这个想法是错误的。恰当的运动是有助于学习的。运动可以帮助学生放松身心。经过长时间的学习，他们非常需要运动一下。放松后，他们可以有更好的状态来学习，这可以提高他们的学习效率。除此之外，学生一般在运动后都可以睡得更好。如果他们睡好了，他们就有更多的精力放在学习上。这是有助于学习。但是，花在运动上的时间过多则会影响学习。