For many - the memories of Sept. 11 are permanently etched in their minds, from where they were to their immediate reactions.
But for those whose knowledge of the event comes second-handedly, how do they view the tragedy?
"Kindergarten (was the first we learned about it in school), I think - there was a lot of emphasis on why we're proud to be Americans, and why we should remember this day," explained Hannah Garcia, a Hays High senior.
Sitting next to Michael Hellmer and Georgia Cardosa, fellow Hays High seniors and Student Council members, the trio shared their experience of learning about 9/11 in their Advanced Placement History course. In that class, they watched United 93 - a film which profiled the passengers and crew on one of the hijacked flights.
"That was definitely a really heavy thing to watch. And it kind of made me feel connected to it as an American," said Garcia.
"If I hadn't watched that movie, I don't think I would have understood where all the planes went, what order they came in, how people found out about it, how there was so much confusion when it happened initially," added Cardosa.
The students shared how they approached the lesson in class that day.
"It was definitely one of those days where right before you even start talking about it, you have to say 'this is going to be a tough day, and everybody's going to have different opinions about it. You have to be really thinking about how other people are feeling when you're talking about it in school. Because no one has the same background, or no one went through the same thing," Hellmer said.
“After not really having any insight of what happened on the plane, I know watching United 93, after the (movie) ended, there was just that silence in the classroom. It felt very heavy in the air,” said Garcia.
“Watching that movie made it a lot more personable – we know what happened, how many people died, what it caused. The whole time I was watching it, I was thinking of my parents, because they’re the same age as a lot of the (victims) in the movie,” said Hellmer, noting their history teacher had a connection to one of the victims on the flight.
As they've grown older, they've learned more about the tragedy - from the classroom to speaking with family members to watching documentaries and old news clips.
It's helped provide context to many issues the country is facing.
"I think it's just as big of a turning point as Pearl Harbor was almost - because it didn't start as big of a war, but I would say 9/11 is the start of the era that we've lived in pretty much our whole lives," said Hellmer.
"It definitely opened up my world. I think we were very closed-minded individuals. Not necessarily completely closed off, but we didn't have the full picture. And then having that, it kind of made us more understanding of what's going on, and gave us a better view of to better tackle and understand these difficult things that happen in our world," said Garcia.
They hope fellow students make an effort to learn about the events.
"Read multiple resources. Go for the facts. Get multiple people's opinions," said Cardosa.
For years, they have observed moments of silence in memory of those were killed. Now they do so with a better understanding of the events that unfolded, the lives lost, and the heroes who responded.
"When you're in elementary school you don't - you know that you're supposed to be quiet, but you don't really understand why. But knowing about it, it definitely makes it a lot more meaningful," Hellmer explained.
"I think it's a day where we don't only remember those who died in that tragedy, but it's also a day where we remember the people that help us, like the firefighters, the police officers, that give up their days in terrorist attacks like this, but also like the hurricanes that are happening right now," said Garcia.