原因：1.考试太滥 2.自身勤奋不够 3.把大量时间用在上网和玩游戏上 4.为了骗取家长和老师高兴
参考作文： At present, a number of middle school students have picked up a bad habit - cheating in examinations.
There are three main reasons. First, schools have given students too many exams, some of which are too difficult. Second, some students are not hard-working and they don"t work hard at their lessons. Third, they waste a lot of time playing games or surfing the Internet. So they haven"t enough time to prepare for the exams. Finally, students have to do so to make their teachers and parents happy.
In my opinion, cheating in exams does great harm to our study. We students should be honest and diligent, and only in this way can we improve our study and make progress. Besides, our teachers should offer us fewer exams and more time to study for ourselves.