CHICAGO (CBS) — Hundreds of students from across the globe were going green Tuesday at a record-breaking community service project in Humboldt Park.

According to the Chicago Park District, more than 450 students took part in the effort to clean up Humboldt Park, making it the largest-ever youth-centered service project in the more than 150-year history of the city’s parks.

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It’s hot, the work is heavy, and Eli McMullen is not being paid, but the Okeechobee, Florida, resident is not complaining.

“It’s fun,” he said.

Neither is Zawng Man, from Myanmar.

“It’s the best experience of my life,” he said.

Those are just two of the 455 teenagers from 47 states and more than 10 countries taking part in a service project to beautify Humboldt Park.

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“These are really motivated young people. Like a lot of young people out there, they want to make a difference in their world around them,” said Cheryl Brenn, director of international programs at HOBY (Hugh O’Brian Youth Leadership) Foundation.

Cy Serrano said HOBY helped guide him out of the tough neighborhoods north of Los Angeles, and into the lucrative world of software development. He started as a participant in HOBY’s annual World Leadership Congress, and now comes back every year to volunteer.

Serrano said if people at HOBY had not believed in him, he “could have been somewhere else entirely. HOBY definitely changed my life, and it’s a big part of who I am today.”

Annie Zhu said she’s only been in town for three days, but is already seeing the benefits.

“Back at my school, I’m a little bit shy, so coming here, I’m kind of getting out of my shell, my comfort zone, a little bit,” she said.

The city benefits, too, as the 1,650 combined volunteer hours put in on Tuesday likely would cost more than $125,000 in paid labor. For the students who participate, their success is not measured in dollars and cents, but future leadership potential.

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“The part that’s been most enjoyable is the leadership skills, because I can already tell that, whenever I bring this back to Okeechobee, it’s going to affect a lot of people in my hometown, and then eventually just be like a ripple effect, and affect the other people else way,” McMullen said.