Why shouldn't cell phone be allowed in schools?

Altough this is a very controverse topic, some people think that it shouldn't be allowed for students to bring cellphones into the school, because it disrupts the learning process.

Most students use cell phones irresponsibly. They use cell phones to talk to their friend during class time. They also use their cell phone to text message or pass on answers to tests, homework, and other class information. Students also use the calculator and camera features in the class, which is another distraction factor.
In addition to disrupting the learning process, the signals from the cell phones can interfere with the school emergency response system. Many schools are banning cellphones because of this issue.

Besides all the 'thinking' it is a fact that cellphones can cause a distraction in education. They can disturb teachers and students. For example, if you were working hard on a piece of work, concentrating hard, and a person's phone rings, it disrupts the whole class. You may become side-tracked or the teacher may be interrupted while speaking to the class.