They thought they were going to religion school. They ended up slaves.

Last year, photographer Mario Cruz received the tip that he had long been waiting for.

He had been documenting the enslavement of children as young as 4 in Senegal. Sent by their families to Islamic schools, or daaras, to become young scholars of the Koran, some were instead forced to beg up to eight hours a day and suffered frequent beatings. Now a source was telling him he could see for himself that the stories about the shackling of students, known as talibes, were also true. There was a school in the city of Touba where he would find children who were chained to the ground to keep them from running away.

Most daaras are genuine in their mission and still provide the education they promise parents. But a decade ago, some of the schools began to abuse the children, poisoning a centuries-old tradition. A 2010 Human Rights Watch study estimated that 50,000 children were being exploited.

Cruz found the school. His translator tried his best to persuade the teacher to let Cruz take photographs but was unsuccessful. So the pair waited. When the teacher finally left for lunch, they snuck in. Cruz found three shackled children, each with a foot encircled by a snug chain that was bolted to the ground. Each had about 10 steps of slack, which was just enough for the children to access the bathroom — a wooden compartment with a hole in the ground.

As Cruz set to work photographing them, the children were at first calm and relaxed. But then five or six older talibes noticed and panicked. The chained children became agitated too and tried to bolt but could only move so far. As the older boys started shoving Cruz, the pair fled and jumped in a taxi. But Cruz said news of his presence had already spread. As they navigated out he saw one road blocked by people holding a cord. By taking roundabout routes, he finally made it back to his home base in the capital, Dakar — a three hour trip turned into six.

Cruz researched and photographed the abusive Koranic schools run by teachers known as marabouts for his book “Talibes: Modern Day Slaves,” which he is funding through Kickstarter.

“I didn’t think that I would see the abuses being committed in front of me,” he said. “I didn’t know for sure what access I would have once I was in Senegal. The first time I saw a talibe being whipped in front of me, I was shocked.”

The accounts of abuse dealt for not bringing back enough money from begging read like a particularly sadistic version of Oliver Twist’s Fagin. Marabouts have been known to beat children with strips of car tires or electric wire as the blood runs — in some cases daily. Sometimes they are beat even when they bring back their daily quota of between $1 and $3.

Some children are even raped by the marabouts or older talibes. According to a prosecutor who spoke to Human Rights Watch, a marabout threatened a talibe victim during the 2014 trial of the marabout’s son for rape. “I will beat you,” he warned the boy in front of the entire courtroom. The child promptly changed his story and the case was dropped.

“Every day I try not to cry. Every day I try not to scream. I don’t sleep. I just close my eyes and imagine myself in a different place. … I know stories about dead talibes, but I’m not afraid of death anymore,” said talibe Amadou to Cruz. Amadou was one of the children who decided to run away and take their chances on the streets rather than face the constant abuse.

Although only 15, he looked much older to Cruz. His hands were weathered. “I really think that he was one of the talibes that really suffered. You can see in his eyes that life was really hard for him,” Cruz said. He found the boy at a dock on the shore of Senegal River in St. Louis, hanging back from a group of street kids who were milling about an abandoned fishing boat.

Amadou was unsure how long he had been a talibe but guessed it was about eight years. And having grown up in the system, he couldn’t remember where he was from or who his family was.

This can be the case with talibes who were sent away as young as Amadou. It makes it very difficult to rehome the children. And a fraction of them are smuggled across the border from neighboring countries like Guinea-Bissau, Guinea and Mali.

The Senegal government has been highly criticized for its slow response on the schools. A law was drafted after nine boys died in a fire at a daara in Dakar in March 2013. It was meant to regulate curriculum and bring uniformity and accountability. But this week, Mody Ndiaye, the permanent secretary of the National Task Force Fighting Trafficking in Persons, said the president had just asked his cabinet to accelerate the draft so that it could be sent to congress for a vote.

Actually, many recommendations of solutions for the talibe problem propose simply enforcing a law that has been on the books since 2005. It criminalizes forced begging and child trafficking. But the rare convictions under the law result in paltry fines and minimal, if any, prison time.

Still, a 2015 State Department report cedes that Senegal is making progress in addressing the issue. The government has implemented a system for collecting data on human trafficking and begun to work in concert with neighboring countries to address porous borders. Ndiaye says the government is training police, social workers and those in the judicial system to increase their knowledge about trafficking.

Ndiaye said that there needs to be more support from communities within Senegal and that part of the blame lies also with parents, religious communities and the media. “All of them are responsible, and they tend to wait for the government to act,” he said in an email. Marabouts and their backing spiritual communities band together whenever one of their own is in trouble, and claim an attack on religion.

“Sadly, I don’t think the marabouts are worried about these images,” Cruz said. “They simply don’t care. They don’t have any concerns about any laws being applied.”