"In order to do well students must be prepared to study outside class time."

It is true that student should be well prepared before and after class so as to do well in exams or tests.
First of all,enough preparation before class can help you to get familiar with things that teachers are going to teach and to find out what you can’t understand by reading books on your own,and then in class you can follow your teachers more easily and pay more attention to those difficult points you have found before.By doing so,you can be more efficient and learn better during the teaching hour.
Second,things that you learn will naturally vanish from your mind unless you can review them at proper time for a few times,so that your efforts before and in class will not turn out fruitless.
Although self-study outside class time is important,the time spent with teachers in class,if well used,is also important,for with teachers’ help your learning may be more efficient,because you can receive images,sounds and other signals at the same time,which can all make a thing more impressive to you.
In a word,in order to be a successful student,studies inside and outside class are both very crucial and indispensable.