Dear Li Hua
I am sorry to hear that you have been punished by school because you take telephone to school.I know you feel puzzled.Here are some advice.
To begin with ,you know that morden phone is useful and convenient.You can chat with friends any time .Or you can play some interesting games to kill time.Also you can use some useful softwares to make study easier such as WO YAO DANG XUE BA,DICTIONARY,TEXTBOOK and so on.
But every coin has two sides.It might be bad for your study sometimes.For example ,some students use it to cheat in test.Some students may play games in class so that they won't pass the exam.It'our duty to try our best to get better grades with teachers'help in school.
In my opinion,you d' better do not take the telephone to school .You need to concentrate on study.
Cheer up!And do better in the future.
Yours
Wang ping