One possible version:
Dear Editor，
I’m a Senior Two student. I’m writing to tell you my opinion on whether middle school students can go to school with mobile phones. I think they can do that, because students can stay in touch with their friends and family wherever they are. Besides, the mobile phone is a way to have fun.
However, there are some problems with using mobile phones. The ring of phones can disturb teachers and students in the classroom. Another problem is that some students can spend too much time and money on phone calls and sending messages.
In conclusion, I suggest students not use phones in the classroom. Also, as it is expensive, the owner should take good care of it.
Yours sincerely,
Li Hua
这是一篇正反观点类文章。文章的要点基本上都以及给出，同学们在写的时候一定要注意选词，要选择一些较高级的词汇如disturb。同时要注意使用一些连接词如besides, In conclusion等让文章更流畅。