The boats quickly sank, dumping the teens in the cold, swift Fox River.
A group of 31 boys from Chicago's North Lawndale College Prep were at Camp Algonquin about 40 miles northwest of the city on the last day of an eight-day trip.
Chaperones were likely asleep when some of the young people launched six paddle boats into the river, fire officials said. It was not clear how many teens ended up in the water about 2 a.m., but at least one of the victims had gone in to help the others.
"Shenanigans," said John Greene, battalion chief of the Algonquin-Lake in the Hills Fire Protection District. "That's what it looks like."
The boats had been taken out of service for the season by having their bottom plugs removed, authorities said.
The trip was organized in conjunction with the Georgia-based leadership group VisionQuest International, said Chicago Public Schools spokesman Mike Vaughn. The school on Chicago's West Side serves an overwhelmingly black and poor student population, aiming to prepare them to succeed in college.
"These are kids that have potential, potential to be leaders," Vaughn said.
He said the school district would investigate how the trip was organized, but it appeared to have an ample number of chaperones, including some from VisionQuest. Camp officials confirmed the number of chaperones had more than met their requirements.
The McHenry County coroner's office identified the students as 17-year-old Melvin Choice Jr., 18-year-old Jimmie Avant and 16-year-old Adrian Jones.
Throughout the early hours Friday morning, rescue teams searched the surface while divers battled the current and debris. Choice, the first pulled from the water, was located at 5:52 a.m. Friday morning, nearly five hours after fire crews were called to the scene, reports CBS affiliate WBBM-TV.
The bodies were all recovered.
At the Chicago school, counselors were on hand to help students, though most of them went home after hearing the news.
North Lawndale Prep Asst. Principal LaCael Palmer-Pratt described the victims as "dynamic young men, which is why they were selected to participate in this program."
The drownings were especially hard for those who knew the students.
"At first, I didn't know who it was," said classmate Jennifer Anderson. "My sister called me and told me who it was and I was shocked. I couldn't cry at first. I seen her cry and it was like ... it all came out."
"It's a rush - it don't seem real to me," Anderson added.
Student Kyra Brown, 14, paused to remember Choice.
"He read me a story that he wrote and got an 'A' on," she said. "It was beautiful."
When parents of the surviving campers heard what had happened, they drove to the camp to get their children.
"The parents - they're just frantic, and they're emotionally upset," said Robert Williams, the father of a camper. "They are over there, and no one is really assisting them in a way that I think they should, and they need to get to the kids."
Hugs were shared and tears shed as the survivors who were on that trip arrived in Chicago.
"They are strengthened in their resolve and coming back as the men that they should be and can be, but this is certainly a difficult situation," said Rufus Williams, board president of Chicago Public Schools.
The students and their parents came to North Lawndale Church for a prayer meeting.
"There's been a lot of pain, a lot of tears, of course, that's been shared," Pastor Wayne Gordon said. "But the content of their time together, remembering some of the moments, it's just a healing time."