I was in the 5th grade celebrating my friend's 11th birthday (he turned 59 today!) when the principal of our middle school interupted and broadcast the radio live over the public address system. We we sent home promptly.
My former parish priest was studying at Holy Cross, classes were cancelled, and the students were called to the chapel for the Trisagion prayers.
Read JFK's inaugural address; I think it's one of the best speeches ever given.