I was a senior in high school. I found out while I was in second-period history. That's the only part of my high school schedule I remember: I had history second period on Tuesdays senior year. The Assistant Headmistress came in and said something quietly to our teacher. He went deathly pale, but kept quiet until the end of class, when he told us what had happened.
That's true for me as well. I had English second period, and that's the only thing I could tell you besides having Physics first period.