ISIS is deploying children as fighters and on suicide missions at far greater rates than previously estimated, according to a new report published in the Combatting Terrorism Center at West Point’s CTC Sentinel.

At least 89 boys died fighting in the name of ISIS from January 2015 to January 2016, according to the report’s authors, three terrorism researchers from Georgia State University. The researchers analyzed photographs published alongside eulogies and found that some of the children were younger than 12 years old.

The terrorism researchers cataloged the images, obtained largely from Twitter obituaries and ISIS’s official Telegram channel, based on 24 variables including nationality, location of death, and the facial expression in the photos used to publicize the child soldiers’ missions. The researchers then went through each photo and determined which pre-set age category—8 to 12, 12 to 16, or 16 to 18—the child fell into.

They used metrics developed by researchers on child pornography as a guide for their efforts.

“There’s a scale in child porn to look at things like facial hair, body hair, pubic hair,” Mia Bloom, a professor and co-author of the report, told The Daily Beast. “Obviously, since these people were covered, we weren’t getting that.”

Instead, they relied on visible criteria like build, facial structure, and facial hair—at least when the children’s faces weren’t covered. They also focused on ratios between different points on a child’s face, which tend to change as a person gets older.

“Your nose and your ears continue to grow through life,” Bloom added.

The new report found that children eulogized online by ISIS in the last year came from countries as diverse as France, the United Kingdom, Tajikistan, Sudan, and Australia, though the vast majority came from Syria and Iraq.

Almost 40 percent of them died by detonating vehicle-borne improvised explosive devices, and 4 percent more carried out mass casualty suicide attacks against civilians. Another 33 percent died as foot soldiers. Almost half of the children are pictured smiling in their final photographs, and many are in fields and meadows—perhaps to evoke imagery of the paradise ISIS believes awaits its martyrs after death, the report states.

But the 89 cases studied by Bloom and colleagues John Horgan and Charlie Winter are just a fraction of children seen in ISIS’s Cubs of the Caliphate video series, which showcases streamlined training camps for the terrorist group’s youngest members.

“We know that the kids go through the process of selection during socialization into the Cubs,” Bloom said. “But we don’t know how these kids in particular were chosen.”

The number of ISIS child fighters is likely larger, as the terror group never details a young soldier’s age in its eulogies, and Bloom’s team has to rely on photographs, which are not always supplied. The team found that unlike other violent extremist groups that exploit underage soldiers for shock value or specialized missions, ISIS overwhelmingly treats its child fighters no differently than it does full-grown men.

Bloom said the report is only the beginning of quantitative research into ISIS’s use of child soldiers, especially as her team found the number of deaths and suicide operations by kids had increased over the course of the year.

The researchers’ outstanding questions include what will become of Yazidi children ISIS is believed to be grooming for suicide missions. (In addition to taking Yazidi women captive as sex slaves, the group may have kidnapped hundreds of Yazidi children for future use in suicide attacks.) None of the children examined in the report appear to come from Yazidi families.

“Either they didn’t promote them on the ISIS propaganda channel, or they didn’t use any of those kids yet. They were just in the training process,” Bloom said.

“If you’re a Yazidi who’s being trained into a suicide bomber, that’s going to take a little more convincing and brainwashing,” she added. “So the question is, will we see it in the next few years?”