Aamani's mother pounded against the car window.

“Wait,” she cried. “Don't leave us.”

Aamani huddled close to her brothers and sisters. Seventy-six slaves had just been rescued from the rock quarry where Aamani and her family worked. The quarry was a dangerous place. Aamani had lost one of her fingers in an accident just the day before.

Now Aamani's mother begged rescuers to stop and save her family, too. The cars halted, and with help from local police officers, the rescuers freed Aamani and her eight family members.

Eight thousand miles away in Green Bay, Wisconsin, brothers Zach and Nate Hunter helped with the rescue. They didn't storm into the rock quarry. They weren't at the government offices where 85 slaves received release papers. Theye don't even know Aamani and her family. Zach and Nate used what they had to help: their voices.

Three years ago, 15-year-old Zach started a campaign called Loose Change to Loosen Chains to help enslaved people. Zach has always enjoyed history and loved learning about people, such as William Wilberforce, Harriet Tubman and Martin Luther King Jr., who helped stop slavery.

One day Zach was riding in the car with his mom, who works for the International Justice Mission (IJM), and he asked her what she did at work. She told him that IJM, a Christian organization, frees slaves around the world. “I had been thinking that if I had lived when slavery was still going on in the United States, I would have been a conductor on the Underground Railroad or something,” Zach says. “I felt the same way when I heard about modern-day slavery.”

In South Asia, where IJM rescued Aamani and her family, nearly 15 million children are slaves. These children work long days doing difficult work at rice mills, rock quarries, brick kilns and other dangerous places. Sometimes they are chained so they cannot escape. They have little hope of ever being free.

After finding out that more than 27 million people around the world are slaves, Zach knew he had to do something.

“When I heard about how slavery was going on in the world, I just thought that was really, really unfair,” Zach says. “I decided to start the Loose Change to Loosen Chains campaign so that I could free slaves.”

Zach didn't do it alone. Nate wanted to help. "I told my friends about my brother's campaign." the 8-year-old says. "I told them it's not right to own someone and make him work all day."

Zach and nate told kids at their schools about their goal to collect change to free slaves. The brothers distributed bright yellow cups, and asked people to fill them with quarters, dimes, nickels and pennies. Zach and Nate found $200 of change around their house. Together, the brothers and their classmates collected more than $8,500 for IJM.

Since then, Loose Change has raised hundreds of thousands of dollars to free slaves. Zach has spoken in front of audiences across the United States and people as far away as Africa, Australia and the United Kingdom have joined the effort. Nate often sits at the booth and talks to people about slavery.

These brothers know that kids really can change the world. “We can make a difference in the lives of slaves,” Zach says. “It doesn't really matter how young we are.”