Eh, it was the 4th. And depending on how you define shooting, could be the 6th.
Just two that I'm aware of. Which are the two others?
Just going off the Wikipedia list. Mind you, all these didn't result in deaths and weren't mass shootings, but:
1/9: A man shot a pellet gun at a school bus full of children, shattering a window. No one was injured.(I didn't count this) 1/20: A student was fatally shot on the campus of Wake Forest University.(Again, didn't count because it was college) 1/22: A 16-year-old male student fired at a 15-year-old classmate in the cafeteria of Italy High School in Texas. The gunman left the school immediately after opening fire. 1/22: Shots were fired from a truck in the parking lot of NET Charter High School, targeting a crowd of students during lunch time. One student was slightly injured, apparently from injuries unrelated to gunfire. One person was arrested in connection with the shooting.(Doesn't seem to be students who fired) 1/23: A 15-year-old male student shot 16 people in the lobby at Marshall County High School and caused non-gunshot injuries to 4 others. Two 15-year-old students died: one killed at the scene, another died of wounds at Vanderbilt Medical Center. 2/1: Two 15-year-old students, a boy and a girl, were shot and injured inside a classroom at Sal Castro Middle School, which shares a campus with Belmont High School. Three other people suffered injuries unrelated to gunfire. A 12-year-old girl was arrested and put in custody.
And then today.
The 12-year-old girl shooting incident was an accident. The gun went off in her backpack. The Italy High School incident was domestic related.