李华因在学校使用手机被学校处分，他感到很困惑，写信给你求助。请根据以下结构提示给李华回信。开头结尾已给出。所给要点必须写到外，自己可以适当补充相关细节。字数：90----100。
Para 1: 手机的优点：联系方便
Para 2: 带手机上学的问题：影响教学，花大量时间打手机有害学习和健康
Your letter reached me yesterday. You said in your letter that ___
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It’s right for school to prevent you from using cellphones in school.