Mobile phone has become a problem for high schools. Some high-school students in Australia are not allowed to carry mobile phones during school hours. Mobile phone used among children has become a problem for the school. Several children have got mobile phones as Christmas presents, and more students will want them. Marry Brown, a headmaster, said that mobile phone was a distraction  to students during school hours and it also gave teachers so much trouble in their classrooms. Teachers were also saying that sometimes students might use phone messages to _ during exams. She said some schools had tried to ban  mobile phones. Some parents felt unhappy because they couldn't get in touch with their children. Many teachers said students should not have mobile phones at school. But there was a good reason that they could leave their phones at school offices. They also said they were easily lost and were a distraction for studies. The passage tells us that   _  .
students shouldn't have mobile phones at school except for some special reasons it is necessary to ban students from using mobile phones during school hours some parents felt unhappy because they couldn't use their phones at home parents should teach their children how to use mobile phones during school hours