For starters, your avg. kid doesn't need a phone that can handle photos. If you keep them on a text-only model, this is one source that they won't have. It won't keep someone from taking a photo and sending it around via computer, but at least that takes a bit longer and requires more effort.
I normally don't keep my phone on while I'm at work, but a few months ago I was waiting for a call from a physician's office and kept it on. I got a text message but being at work didn't bother to look at it immediately because I knew that wasn't the call I was waiting on. Twenty minutes later I got a regular voice call. When I answered a male voice purred, "Well, what do you think?" I knew it wasn't DH's voice, and he doesn't call my cell at work, so I knew it was a wrong number, and I said so.
You should have HEARD the panic in the guy's voice! The conversation went like this: "OMG, do you have a camera phone?" Yes, I say. "Did you receive a text message a little while ago?" Yes. "OMG, I'm SO sorry. I got this number from a girl in a bar last night -- guess that wasn't you, huh?" No. "OMG, PLEASE just erase that message, OK?" By this time I am DYING to burst out laughing, but I controlled myself; the idiot deserved to think I had seen the photo.