The Journal of Quantitated Criminology ran a very large study on gun bans in the US. For starters, the US is very different than other countries when it comes to gun control: The same methods do not have equal effects. In the US, gun bans have a negative (bad, not -) effect on violent crime. The wide commercial availability of weapons acts as a powerful deterrent. Also, when guns are banned, the black market starts selling them in much higher quantities. This means that mentally ill people can buy guns more easily.

I believe it is obvious that younger people should not be trusted with weaponry, and I see no reason why they need to be concealed on campus (in a college campus in this case). However, being allowed to open carry pistol on a campus could be an effective deterrent as long as the owners of the guns take many classes and know what they are doing.