CEDAR FALLS --- Bob Schmidt's sophomore history students were full of questions.
Why did the terrorists target the World Trade Center? Why not more historical buildings?
How did the suicide bombers get on the planes?
Why did people jump?
How did others get out of the buildings?
In the days leading up to today's 10th anniversary of the attacks on the World Trade Center and Pentagon, Schmidt took time out from traditional U.S. history lessons at Cedar Falls High School. Instead, he talked about what happened that morning and the fallout of those events.
His students had a lot to learn.
"This is one of the first groups I've had where this was more of a historical event," Schmidt said.
The question of when an event becomes history depends on who you ask, said John Johnson, a history professor at the University of Northern Iowa.
"The sort of old-fashioned view is you need a great deal of perspective, and you probably should give a significant event like 9/11 quite a few years," Johnson said.
"I feel different. I believe the more modern view is the morning newspaper or the latest tweet is history," he added.
"I would rather have professional historians weighing in on recent events along with everybody else, rather than saying, 'As a historian, I can't say anything for 10 years.'"
Schmidt, who was teaching history in Cedar Falls on Sept. 11, 2001, started talking about the event as it unfolded on television. His students asked questions about what they saw, and he did his best to provide answers, though some turned out to be wrong by the next day.
Johnson said that's OK. History is often reinterpreted and revised. Early versions might not be exactly correct, but that doesn't mean they shouldn't be talked about.
"Revisionism is a reality of history, and it is one of the beauties of history because every event will mean different things to different generations and be looked at from different angles," he said.
Debbie Lee, the secondary curriculum director for Waterloo Schools, said the passage of time allows people to "review the impact of what happened ... how lives changed, how the economy was affected, how politicians respond to current events, how international relations were impacted, how the event connects to other events, etc."
"This then becomes the focus of teaching and learning," Lee said.
There are students who are interested in history. They may not have lived through the Great Depression or Pearl Harbor or the President Kennedy's assassination, but they want to know more. There are just as many who couldn't care less about events that shaped this country and its people.
For this generation, some of that changed on 9/11. They watched events unfold, and they experienced a historical game changer, Schmidt said. And that changed the classroom dynamic.
History lessons about Sept. 11, especially in the early years, were different. Almost everyone was engaged in the classroom discussion. Johnson's students, most whom are between 19 and 22 years old now, still remember where they were when the towers fell.
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They offer thoughts and feelings about the day. They want to talk about it, though sometimes the conversations can be emotionally and politically charged.
"Ten years ago is about when many of them started thinking real thoughts about society, so 9/11 is a date that they remember," he said. "... Their reactions are part of the story."
For several years, Schmidt said, his high school students brought just as much to the table as he did. They could fill in details about when, how and why.
As time passed, the students who remember the day become more sparse.
"I showed a tape in class last week and was very surprised, certainly taken aback, by how few students had knowledge of even the sequence of events," Schmidt said.
But their interest is still piqued when the topic comes up in class. They want more information.
"It's more interesting because I did watch it on TV," said Jacob Pence, a sophomore at Cedar Falls High School. "When it happened we were alive. But we don't know a lot of the details."
Johnson's recent U.S. history class for college students focuses on events from 1960 to the present. Schmidt's high school sophomore class has a broader focus, encompassing history from 1940 on.
Both use textbooks, though Johnson does to a much lesser extent, to help students wade through the historical topic of the day. But when it comes to Sept. 11 discussions, the teachers agree textbooks still leave a lot to be desired --- and they may never be the preferred teaching method for truly modern history.
"You have so many more documents in the broadest sense of the word. Besides the obvious newspapers we have various digital accounts and any number of visuals of what happened. Then there is the commentary that is itself part of the news," Johnson said. "It is more a question of what do you include because there is so much you can talk about."
Johnson has his students delving into the Sept. 11 Commission documents. Schmidt uses a Smithsonian documentary to supplement his course.
Some of the information can be gruesome. Some can be provocative. And some --- especially the commentary --- is politically charged.
That doesn't stop them from teaching it. Schmidt's students saw and asked about the people who jumped from the upper floors of the burning World Trade Center towers. They called the images "disturbing," just as their peers did 10 years earlier.
Schmidt remembers watching the attacks on 9/11 with his students. The usually too-cool high school students were leaning on him for support, and he had to be both history teacher and counselor.
"They wanted answers. They wanted me to make sense of it and tell them it would be OK, but that was hard," he said.
He did his best to allay fears without offering too much of a false sense of security.
His daughter walked into the room just as the third airliner hit the Pentagon. She was scared. She needed her dad, not a history teacher, Schmidt said.
"I just remember mouthing, 'This is not good,'" he said.
Schmidt wanted his daughter to be aware of the severity of the situation, but he didn't want to alarm the rest of the class.
It was a difficult day to be in the classroom. It was a difficult day to be an American. And for many, reliving those days, even if they were only a child at the time, remains difficult.
"It is one of the hardest things to learn," said Lara Heatherton, a Cedar Falls sophomore. "It's hard to watch those videos. You wonder how all of that could happen in just one day and have such an impact on the country."