How Frequent are School Shootings?

I find that since I have been threatened I have an increased interest in school safety. So, I am going to look into school safety. I've spent some time today looking at what the web has to offer on school violence. I stumbled across a website called Info Please at www.infoplease.com/ipa/A0777958.html . It is pretty interesting. If you have an opportunity check it out. The company that runs the website, Pearson, has been publishing statistics since 1938. The website has listed all of the school shootings around the world since 1996. In addition they have also listed how many people were injured or killed, who did the shooting, and the age of the shooter.
What I found to be eye opening is that there are a lot more school shootings that one might think. Prior to this research I could have perhaps come up with a handful of school shootings that I had heard about. Columbine, of course; the shooting death of a six year old girl in Flint several years ago; the rather recent Amish school shooting; and two others that I remember watching on the news but couldn't give you any details on. Well, I read through the timeline of school shootings on Info Please. I only counted the shootings at middle and high schools in the United States. Since 1996 there have been roughly 36 school shootings in the US. Of that 36, 14 of the shootings involved principals, teachers, or other adult staff members. This means that about 38% of school shootings have involved teachers/administration. This is by no means a scientific study. It's just my observation.
More disturbing is that almost without exception the school shootings have been committed by students within the school, not outsiders. There were a couple exceptions, like the Nickel Mines shooting at the Amish school in Pennsylvania. It hit me- all of the standard security precautions that schools take wouldn't do much good against a threat from within. What good does locked doors, visitors signing in/out, or having security cameras to monitor activity in the school really do?
I then went to You Tube and found a student production entitled School Safety 101. This is a 9 minute film that interviews high school students at Bixby HS regarding how safe they feel at school. I thought the students would downplay the importance of safety. I also thought that most of them would say they feel safe. However, most of the kids said they did not feel safe. Furthermore, they felt that their school administration was powerless to stop a shooting. The filmmaker, Kendal Osborne, looked at how safe the students felt by doors that required a security code in order to enter. The majority of the students interviewed thought the security coded doors were a joke since codes were initially posted outside the doors. One student pointed out that the doors might be a hindrance to police if they ever had to respond to a school shooting there and didn't know the code to get in.
I learned a lot more about school shootings than I had known before. I have no idea we have had so many in this country. Check out the website and You Tube if you get a chance. They are both enlightening.