I agree with the maturity issue. As for where/when to carry, this is a calculated risk unfortunately. I also fall into the category of "would rather face legal charges than hospital charges" for myself and my loved ones. Fortunately, there is a pepper spray that is really effective and doesn't scream "hey I'm pepper spray" to either bad guys, or medelsome teachers, or school officials. Its called the Key Defender and its made by ASPn the same people who make the expanding batons for police. It looks like a standard kuboton externally and the pepper srpay comes out a hole in the business end. The trigger is a plunger in the other end and has a positive almost fool proof saftey. I say almost fool proof becaue I accidentally left my keys in a gas station one day when I was getting a ride to work (the fact that I wasn't driving is important because if I had been driving, I wouldn't have left my keys with it on it at the gas station.) When I figured out where the keys were, I called the station and the clerk was a bit upset because he had played with it and released the spray and cleared his store out for about an hour.
The great thing about this configuration is that it has a key ring on one end, this helps ensure that you have the spray in your hand when you might need it. It also allows it to double as a flail and a pommel striking device. Since it is a kuboton, it can theoretically be used as a pressure point and joint manipulation device though I think the pepper spray is usually more effective. It comes in multiple colors, textures and sizes. And another really great thing about this is that its not one time use, the kuboton unscrews from both ends and refills are available. Even cooler is that they also sell a pressurized water version for use as a training cartridge. It may not be the absolute best for everyone and all situations, but it is a hard to beat option for a low profile, effective and ergonomic method of carrying pepper spray for minors. You can find it online and usually at gun shops and law enforcement supply stores. Hope this helps.