Personally, I against the idea of allowing students to bring mobile phones to schools. I believe schools have enough public phones and in case of emergency, the school management or teachers will be able to contact parents immediately or vice versa.
I certainly hope that there will be no misuse of mobile phone by students to go againts their teachers and other students. Imagine secretly capturing photos or videos while their friends are being punished or teachers punishing or scolding their students, then put them up on their blogs or distributing them through mms.
School management must be very strict on this matter and not to allow students hiding behind their desks sms-ing while the teacher is teaching in front of the class. Also never allow them to disrupt the class(es) or any part of the school with those irritating ringing tones.