I was in High School. Couple students had cell phones at the time and texts started coming in fast which at the time was rare due to cost. Couple mins later the principal made an announcement that the world trade center has been hit by two planes and the school was on lockdown.
We had a substitute that day and they decided to keep teaching. I walked to the back of the room wheeled the tv to the front plugged it in and turned on the news. Sub stopped yelling at me mid sentence when we all saw the images of the towers in smoke.
My demolition expert father was having surgery that morning so I left school early to go visit him. Was very interesting listening to a bunch of construction/demolition experts talk about the collapse.