Jeff Parness hopes to nourish a volunteer spirit by telling schoolkids about Sept. 12, 2001 — “when people came together to help each other recover.”

“People from small towns and big cities went out of their way to be with us in our darkest moments,” said the West Side dad. “That spirit of selflessness and volunteerism was so much stronger than the terror [of] the day before.”

Parness won a 2007 Liberty Medal for starting the New York Says Thank You Foundation, which annually takes volunteers to work on a rebuilding project at a US community hit by a natural disaster.

It’s now finishing up a project that takes a giant US flag found shredded near Ground Zero to each state, where people add stitches and pieces of retired flags to make it whole again.

The National 9/11 Flag, which includes a piece of the flag Abraham Lincoln was placed on after he was shot, is to be part of the 9/11 Memorial Museum.

“It’s all about how you transform a tragedy into something hopeful,” said Parness, who hopes a documentary about the nonprofit that recently premiered at the Tribeca Film Festival will inspire kids to volunteer.