Should students be able to snap a photos on their cell phone at school? I believe not, as it invades privacy if the anyone in the background is captured. Its like taking a picture though the person does not have the will to decline, especially if it manages to get online, "once on the web, stays on the web". Now I can understand if they where right in mind and manage to snap a photo of just themselves, that would be perfectly fine, yet as a growing society we just don't see the leading importance of our or others privacy. I would go half way of denying that option in schools, other than the main factor is, we shouldn't even have cell phones at schools (Note referring to k-12 schools in the US) in the first place.
But, the simple thing is, students shouldn't even have the cell phone on them in the first place, that's why the school provides other means of communication at their offices. Typically, schools state that its a rule not to bring them, though we need to be more harsh on consequences if one is found. Now this is for taking photos such like Snapchat/Instagram, It is totally understandable for a parent to arrange their children a cell phone for daily communication before and after school.