Newtown High School held its graduation on Wednesday, celebrating a class that would have included 20 students who were killed in the 2012 shooting at Sandy Hook Elementary School.

"They're stuck in time as children," says Katie Bisset, who was a third grader at the school when the shooting happened.

Her twin sister, Lexi, was in the building too, and says she woke up thinking about her schoolmates.

"They left this world knowing that there was hope for them to do everything that they wanted," she tells News 12, "So, I just like to think that they would have accomplished all those things."

It was that thought that Lexi says brought the Bissets to the shooting memorial on graduation day, to drop off a letter.

They say, as far as they're concerned, those 20 students also graduated on Wednesday. Lexi "thought it was only right as a classmate and a friend to just write a few words congratulating them for graduating with their friends."

Katie says with all the support from the community, she feels that "even though they're not physically here, they're spiritually there, and surrounded by so much love, especially in this town."

But that love has also led to frustration with Washington D.C. Both sisters say days like this are a reminder that nearly 12 years later, the country has not passed any sort of meaningful gun legislation.

It's a thought that Katie says sometimes make it "really hard to have hope, but it's days like these when we come (to the memorial) and we remember and we know that they would have been so happy and proud of the people that they would've become.”

The Bissets try to live that way themselves, with Katie majoring in environmental studies at Siena College and Lexi, getting her degree in business analytics at UConn.

"I always tell myself I'm living my life for them," Katie explains. “We get to go to college, we get to do all these incredible things for them, in honor of them. So it's a sad day, but you also have a little bit of pride."

The twins hope the other graduates will feel that pride to, and take a piece of Sandy Hook with them wherever their next chapter is.