There was a time when morals were taught in schools. How many shootings took place before 1963 when Madaline Murray got any mention of religion taken out? When the religion went, so went the moral teachings.
Lots. No more statistically than there are today. In fact, crime in this country is at historic lows and mass shootings have been flat for years. The only reason it seems more common is because of the 24 hour news cycle/Facebook/Twitterverse.
Having government employees teach the Bible is not an evidentiary cause of any of this.