Same here, only earlier this year.
There were two notes found at my high school threatening to go on a shooting spree on a certain date. Sad state of affairs, really. Anywho, police were on constant guard, and we were able to choose if we wanted to come to school or not.
I live not too far from the Red Lake Indian Reservation Shooting here in Minnesota, and now gun drills (lock downs) are performed in middle schools and elementary schools in Minnesota because of it.