If the teacher didn't come， the students wouldn't study hard at all， some were passing notes， some were tearing off the paper in the workbook and folding the airplane to play， some were secretly sitting down and moving the chairs to other places， and some went too far， and went to the podium to play with the chalk newly bought by the teacher， even if the class cadres went up to manage the order， it would be useless. Of course， there will always be students who love to snitch and report to the class teacher. Those naughty students have been criticized by the teacher several times， but they are not to be outdone. This time， they vowed to study hard in the future， and may do it again next time.

　　If the teacher's footsteps are heard at the door， the students sitting by the window will give an "ok" gesture， which is a good secret code colluded with the naughty boy， representing "the teacher is coming". At this time， the naughty boys pretended to study hard. The teacher came in， looked at the students who were doing their homework carefully， and nodded with satisfaction.

　　This is why the classroom is sometimes noisy and sometimes silent. Are you satisfied?

　　如果老师没来，同学们根本不会认真自习，有的在传字条，有的把练习册的纸撕下来折纸飞机玩儿，有的偷偷下座把椅子搬到别的地方坐，有的更过分，跑到讲台上玩老师新买的粉笔，即使班干部上去管理秩序也无济于事。当然，总会有爱打小报告的同学“蹬蹬蹬”跑下去报告班主任，那些顽皮的同学被老师批评几次还不甘示弱，这次发誓自己以后一定好好自习，可能下次还是再犯。

　　如果门口发出老师的脚步声，坐在窗户旁的同学会比出一个“ok”的手势，那是和调皮鬼一起串通好的暗号，代表“老师来了”。这时，调皮鬼们也装作认真学习的模样，老师走了进来，看了看都在仔细写作业的同学，满意地点了点头。

　　这就是为什么教室里，有时喧闹无比，有时寂静无声的原因，你们还满意吗？