Gunsmoke and Mirrors: Have there really been 74 school shooting since Newtown?

"Sure, Jimmy, technically it's not a
gun. But we'd still better get the
Hell outta here before they
add us to the list."

I randomly selected and investigated 10 of the alleged "74 school shootings since Newtown"--a claim that has been lighting up the Internet like tracer rounds. I came up with one shooting that actually fits the description of what we think of when we hear "school shooting"--a middle school student shot two other students in school on a school day. Here are the other nine incidents:
20. Two custodians shot by third custodian late at night.
23. Five-year-old brings loaded gun to school in his backpack and it discharges.
27.  A 19-year-old man kills himself in a high school parking lot on a Saturday.
28. Two teenagers get shot outside of their school after a fight broke out. Police say it was part of an ongoing dispute.
33. A football player is shot on a high school campus on a Sunday, presumably by someone from a rival team that they had had an altercation with.
37. Four gangbangers try to rob a teacher in a classroom at 7:00 p.m.
49. A high school girl is shot in the butt by a gang member she is acquainted with while standing in a school parking lot after a basketball game. She is refusing to cooperate.
54. A guy kills another man in his car parked in a school parking lot.
55. After a group of students is accosted by a gang outside an off-campus restaurant at 2:45 a.m., someone fired at the dorm building they lived in.
I don't fault people trying to draw attention to the issue of guns in schools. But generally speaking, you're not doing your cause any favors when you so obviously overstate the problem.