Cell phones in schools a bad idea?

I personally feel that cell phones in school is a good idea. People say that cell phones can do a lot of negative things but honestly I disagree. Now I am speaking from a students point of view so you know I'm already going to disagree ith this matter. They say it is going to lower students grades which I disagree with. Also, what if there is an emergency at school where nobody is around and you need help, what do you do? It's just things like that that make cell phones a necessity in school. Another reason why a cell phone is a good idea in school is because for example, I am in a web 2.0 class and my teacher wants to have class somewhere else. He would send a twitter alert straight to my phone and I would know not to go to the normal classroom for todays class. Cell phones can be a good resource of information as well. That is why I feel that cell phones staying in school is a good idea and we shouldn't ban cell phones in school.