I was a junior in HS at the time. I remember EXACTLY where I was when I first heard about it. It was right before school started, I was in the hallway in front of our HS office, talking to my HS baseball coach about the game that night. A kid came up to him as was like "Hey Fulls, a plane just crashed into the World Trade Center". My first thought was a Cesna or something, and it wasn't a big deal.
My first class of the day was Trig, and our teacher at the time was in his last year before retirement, so he turned on the TV, and said that he wasn't going to teach that day.
Right before the first tower collapsed, our HS principal got on the overhead system, and told all the teachers to turn off the TV's and to continue teaching, because "the event is in New York, and not Wisconsin". I'm still a little bit bitter to this day because of that.
So our teacher turned off the TV and started teaching. Then he stopped 2 minutes later and said "screw that, this is important" and turned on the TV again. That was right after the first tower collapsed.
Between classes, is when the 2nd tower collapsed. So I never actually saw them go down live.
9/11 is still a part of why I became a firefighter, and is why I am SO passionate about it. My captain when I first started, personally knew many of the firefighters that died on 9/11, and instilled how important of a day that was.