web 2.0 guives a lot of tools that can be use with cellphones, I think that if students persist usign them in class, you should stop making of that a problem but using tools like twitter to develop some activities, not the whole class but if students see that it's not prohibited they probably stop doing it, specially teens.
I think that there is a period where it's better to separate for instance boys and girls since when 11-13 girls' tend to learn faster while boys are still slow, I've worked as a teacher and that's why I say it. but a complete isolated educational process is really dangerous to develop social interactions.