I was in 8th grade, Catholic school. They began piping the radio news into the classrooms through the PA system. About half an hour later, we heard the official announcement that the President had died about the time we started listening to the radio news. I remember being a bit angry and bewildered because they didn’t tell us of his death as soon as it happened. School was let out shortly after that.
Other than that, my own reaction was just numbness from the shock.