Mobile phones in schools?

In many schools, children have been banned from taking mobile phones with them. Yet in others, they encourage it. What are your views?

Many teachers argue that children sit sending texts, playing games and even making calls in their lessons. This causes a disruption from their teaching and causes children to miss out. They say that confiscating the phone does not simply do the job as they are often argued with and cannot obtain the phone.

Other teachers suggest that youngsters need the phones in case of an emergancy. I know that when i was in school i contacted my parents almost daily. Whether to confirm times for being picked up or to simply let them know you would be late home.
What if there is a real emergancy? Would any of the teachers on the con side of children having mobile phones, be able to live with themselves if one child was harmed because they couldnt get hold of someone for help?