I was in Catholic school at the time as well.The principal came on the PA system at first and announced to us that "something terrible" had happened but she couldn't tell us what it was.For some time we were left in suspense and were pretty scared (7th Graders we were).The whispering that ensued was regarding nuclear war! Every time we heard an airplane fly over we thought it was going to bomb us.
Just as was the case with our parents generation regarding Pearl Harbor (or FDR's death) we'll never forget where we were when we learned about JFK...or 9/11.
We had that kind of scare when JFK decided to stare down the Russians over missles in Cuba.
The nuns rounded us up and sent us home early.
Every jet passing over was noticed.