According to the survey recorded in the book named Our Underachieving Colleges. Just 20% of the content of class lectures was remembered by students after a week.
It turns out the necessity of the extracurricular activities should be paid more attention in our daily life. As it can obtain what we can not recognize from book in the classroom. Such as friendship built in the activities, problem solving skills. It also have a benefit of open-minded.
Just as the saying goes, all work and no play makes Jack a dull child.