Teaching on this 9/11 was an exercise in pivoting: talking about the terrorist events 24 years ago, as well as the events of 24 hours ago.

"People no longer talk about their differences," Rob Wills, a teacher at Cardinal O'Hara High School in Springfield, Pennsylvania, said. "People right away go to fighting."

Wills has taught for nearly three decades. Across the hallway on the third floor of the Delaware County school, Marisa Linsky was also hard at work. 

Linsky has taught at Cardinal O'Hara for four years. Both teachers — like so many others — are adjusting history and government class lesson plans.

Wills was at O'Hara 24 years ago.

"I remember it vividly, yes," he said. "And then all panic breaks loose. Parents are pulling up here in the front, pulling their kids out of here."

Linsky was a young child on 9/11. The teachers are from different generations, but spent Thursday making sense of the sharp political division following the fatal shooting of Charlie Kirk, on a day when many Americans remember the nightmare that led to historic unity. 

"The fact is, you better learn to respect people with different opinions and different ideas," Wills said. "That's why we have the political system we have, because sometimes you win, and sometimes you lose."

Linksy said she encourages her students to be engaged.

"I think it's really eye-opening for them to see how much actually does impact them," she said. "About things like gun control, about the different laws that are taking place across our country, the way Congress works, the way the president works."

Both teachers had about a half-dozen classes combined on this Sept. 11, navigating difficult current events and emotional memories.

"I think every generation gets one day that's just burned into your memory," Wills said. "I think my grandparents, it was Dec. 7. I think my parents, it was Kennedy's assassination, I think my generation was Sept. 11, and I think God forbid, with this generation, I don't know what they're going to have."