NEW YORK, N.Y. — Sept. 11 is an important topic in classrooms across America leading up to the 20th anniversary of the attacks.

Over time, teachers' classrooms have become filled with students who were not alive in 2001. In fact, more than a quarter of Americans were not yet born when the attacks happened.

"We have students now who have no lived memory of it, and from what teachers reported, very little information about it and in some cases, sort of misinformation or misunderstandings of it," said University of Wisconsin-Madison Professor Jeremy Stoddard.

Stoddard has researched how 9/11 is being taught in schools. He helped lead a survey asking teachers what they think could be done better when teaching about the attacks.

Stoddard found in many schools, Sept. 11 is often only talked about around the anniversary and lessons don't go beyond the events and heroism of the day.

“We learn from the past to avoid some of the mistakes in the future, and frankly we’re not very good at that, partly because we tend to simplify, U.S. history in particular, into sort of this story of freedom and progress," Stoddard said.

While it's important to talk about the lives lost and the heroism of the day, Stoddard says lessons need to contain more historical context and look into what led up to the attacks and examine the impact 9/11 has had on the world today.

"Really thinking through, what is the goal of 9/11? One of the dangers of the sort of simple, collective memory issue or story around it, is when it comes to things like leaving Afghanistan, or the proposed Muslim travel ban from a couple of years ago, you can only really understand that thoroughly by understanding the context of 9/11," Stoddard said.

Stoddard is one of the people behind a website that provides resources to teachers that can be used in lessons about the 9/11 attacks.