There are stats and lists all over the place. There’s no upward trend in school shootings, the deadliest school killing is still the 1927 Michigan school bombing, and as far as safety is concerned, a school is still one of the statistically safest places a child can be.
http://left.wikia.com/wiki/School_Shooting_Timeline
Scroll down to 1966 at the bottom and read your way up. There are a few incidents with gaps of years until you get to the 90's and incidents increase greatly with steady occurrences.