I was in the American Midwest, and the first I heard of it was during first period a teacher came in and asked to take the TV (one of those big CRTs on a trolley) to watch something on a "bombing of the World Trade Center".
It was when I went into the next period I learned that the previous teacher wasn't talking about the '93 bombing, but what was going on that day - I was in time to watch the second plane hit. The rest of the school day alternated between teachers who tried to keep things normal and those who gave over to us watching the news.
I had driver's ed class that evening, and just before I went there was 2 loud booms, and by the time I got to class, there were rumours that the nearby military base or a local hospital had been hit. It was sonic booms from planes taking off from the military base, though why they were taking off in the late afternoon, I'm not sure. I imagine many places in the States near military bases have similar stories.
I spent the rest of the evening with the news on while writing papers for English class and talking with friends online from all over. I was in an online writing and roleplaying group and a few members were from New York so it was all watching for them to get on.
The next day, the school seemed divided between those wearing peace imagery and those wearing military ones, but it all quickly fizzled out.