Pretend there are no religions, no gods, and no laws that prevent you from killing. Would you behave any differently with regard to killing than you do now? Why or why not?
Let me just cut to the chase. There are a number of psychological exercises including and similar to the trolley problem.
Basically, these exercises examine the subject's intuitive ethical sense in a way that is not related to morality. They can be fiendishly complex. For example: a runaway train is headed down the track. You have control of a switch. Currently, the train is heading toward a mother pushing her infant child in a stroller. If you flip the switch, it will instead hit five single, adult men. Do you flip the switch? What if the train is originally headed for the five men? Do you flip the switch? What if they are convicted petty criminals? Convicted murders? What if it were one innocent man instead of five? An 85 year-old man, specifically. What if it's one innocent man on one side and two petty thieves on the other? How would you feel about someone else who chose to flip the switch, or not, in each situation? I think you'll find thinking about these questions that you have an inherent ethical sense unrelated to religion or morality. Pay attention to your reasons for your answer in each case.
My point is that there are no blanket statements like "this is what happens when you take God out of schools" because it's just not accurate. Would a more faith based upbringing benefit some? Sure. Would it help some stay a virtuous course? Sure. Is it a guarantee? Nope.
Not to mention that religion isn't actually a solution unless you can find a way to force people to believe something. If they don't want it on their own, it's pretty much out of contention as far as causality.
***On a side note, thank you moderators for letting this thread stray close to the line. Everyone's been respectful but I appreciate you folks letting this one hang around.
As to the second bolded part of your post, there really is no way to focus only on quantifiable things because many factors that influence a person to act violently are simply not quantifiable. However, that does not mean that these things have no influence for good or for ill. Therefore, since we cannot quantify everything, it makes sense to consider some things that may not be quantifiable but may still have an impact, such as religious and moral upbringing and the ability to freely exercise your beliefs without fear of Government restriction.
Having said that, I am not saying that religion is the only answer. Obviously it is not. But I believe it's a huge mistake to exclude it as part of an overall strategy, if you will, for dealing with the violence which has become so pervasive in our society.
WHile on this subject, am I the only person who is upset that Christmas is a Federal Holiday and other religious holidays such as Ramadan, Hannukah, Dasara, and the holy days of other religions are not? I am not a Christian and it is ridiculous that companies are forced to pay overtime or close or respect this holiday over others. I am sorry but I get riled up about it. Either we honor them all or we don't honor any of them.
As far as prayer in schools, the kids can do it on their own. We don't need an official moment of silence or moment of prayer. If the magic Skygod of some silly cult gets offended because I don't want a school sanctioned Bible or Torah study or moment for their invisible supreme being that is not my problem. I do not have a problem with kids or faculty praying, I have a problem with the school sanctioning it. They can do it on their break or lunch or whenever but not on my time. I pay for the schools with my taxes and I don't want to pay teachers to pray.
I've got no problem with God in schools or anywhere else for that matter. Just don't let it run around unsupervised.
The problem with the world is grown-ups behaving like unsupervised children.
If we know that one can follow a religion and still do evil things, then what will putting religion in schools do? Nothing. In the same way that a child growing up in a religious home can do evil, so can a child growing up in a school system that teaches religion. It is not a solution.