article: It's the lunchtime break at Shanghai Xianxia Middle School. No mobile phones can be heard ringing anywhere. The common sight of crowds of children chatting on their phones or sending short messages has disappeared .
  A grade-2 student said: "I couldn't concentrate  during classes if the phone was with me. I couldn't help checking if there were messages or missed phone calls. I even played games on the phone sometimes."
  The school leaders say they feel the ban  is necessary to keep order in class. They even gave out an open letter to remind parents not to let their children bring mobile phones to school. More than 96 percent of parents say they welcome the school decision. The school is also being flexible in _ the ban. Those students who live far from school are allowed to bring mobile phones to call their parents. But they still have to turn them off in classrooms.
  Medical experts  have also welcomed the school decision. They say too much dependence on mobile phones can cause many psychological problems in school students.
question: The passage mainly tells us about  _  .
options: whether the mobile phone should be used at school by students the harm the mobile phone may cause to middle school students different opinions between school leaders and medical experts a ban on the use of mobile phones by students in a middle school