Thousands of homeless children across New York City will be getting backpacks just in time for the upcoming school year, thanks to one city organization.

Volunteers of America Greater New York expects to hand out 20,000 bookbags stuffed with school supplies to kids in need.

“These are kids who don’t get a lot of new things, and you can see the happiness on their faces,” said Rachel Weinstein, who founded the program dubbed “Operation Backpack.”

While working with homeless shelters, Weinstein said she would notice schoolkids heading to class with only what they had in their pockets.

“I can remember seeing children getting on their school bus like that …,” she told The Post. “I would see them doing this after going shopping for my own daughter and getting her whatever she needed.”

Even very young kids are aware that they have less than their peers, and “it can be really damaging to their self-esteem,” Weinstein said.

Over the last 16 years, the program has handed out 180,000 supplies-stuffed satchels to struggling children, with the help of corporate sponsors and volunteer donations.

A recipient of one of the schoolbags — who is now a 22-year-old college student — credited Operation Backpack with rebuilding his sense of self-worth.

“It just showed that someone cared,” Bakary Diallo said. “And it gave me what I needed.”

Diallo lived in a city homeless shelter in high school and recalled the shame of showing up with little to nothing, while other kids reveled in their new gear.

“You start to think negatively,” he said. “It puts you in a dark place right from the first day.”

But after being outfitted with a new backpack, Diallo’s talents blossomed – and propelled him to Daemon College in Buffalo.

The initiative not only relieves strapped students – but also city teachers who often dip into their own wallets to help needy kids with basic supplies.

With those materials already provided, they’re able to funnel their limited funds elsewhere.

Each year, at a special ceremony, thousands of program participants pour into a warehouse to select their perfect bag and personalized materials.

“When you don’t get a lot in life, it’s like Christmas for these kids,” Weinstein.