And they are concentrated in the city schools most likely to struggle: large, comprehensive high schools.
The report carries "pretty big implications," said Lori Shorr, the city's chief education officer. "A public school system is only as good as the outcomes it achieves for its most vulnerable students."
The data were collected for the School Reform Commission, which last year asked Shorr to assemble a working group to get a fix on a question that, surprisingly, had never been answered: How many Philadelphia School District students had ever had contact with the child welfare and juvenile justice systems?
Citywide, across all grades, 17 percent of students have been involved with DHS or the juvenile justice system, the Children's Hospital analysts found. By high school, that number grows to 20 percent, and nearly half of all district high schools have more than 100 pupils or more than 20 percent of the student body involved with DHS.
David Rubin, a Children's Hospital pediatrician and codirector of its PolicyLab, said he imagined a typical high school classroom, where perhaps a dozen young people in a class of 30 might have complicated needs arising from a life in foster care or problems with the law.
"In a very challenging financial environment, it helps us understand what these teachers face every day," Rubin said Tuesday at a news conference at district headquarters.
Students involved in the DHS and juvenile justice systems need social and emotional supports often in short supply or absent in the city's strapped public schools, which often lack full-time counselors, nurses, psychologists, and social workers.
Anne Marie Ambrose, DHS commissioner, said the report would help cut through that.
"This is a guide for additional investments that DHS is going to need to make in classrooms," she said. "We have a tremendous amount of work to do."
DHS had already placed social workers in a few schools and hopes to add 27 more throughout the city, Ambrose said. The agency has also had to scramble to cover programs that had previously been administered by district staff, she said, including a truancy program that had been administered by school employees who have been laid off.
Superintendent William R. Hite Jr. acknowledged that the district's resources may be limited - at his suggestion, SRC members recently refused to pass a budget because they believe it does not contain adequate funding to run the school system - but said that if necessary, funding must be reallocated.
Hite also stressed that outside partners such as DHS and the city will be leaned on increasingly to provide social and emotional supports.
All students must have a shot at success, Hite said, "and that means all. It doesn't mean all except those who have previous involvement with DHS and juvenile justice."
The analysts found that some DHS- and juvenile justice-involved students are thriving, in many cases because they have found niches at schools. One student the researchers followed attends a large comprehensive high school but is involved in an automotive technology program, and another finds meaning in a dental-hygienist program at another city school.
"We've got to figure out how to make that happen for more kids in more places," Shorr said.
Roberta Trombetta, acting chief executive of a charter school in West Oak Lane for students in foster care, praised the report and agrees that those in the child-welfare system need additional support.
"I think it's great they're shining a light on these issues," Trombetta said.
She said the report should bolster the case of her school - Arise Academy Charter High School - as it fights the SRC's efforts to close it on academic and financial grounds.
"This supports the work we are doing," Trombetta said. "Kids in care need social, emotional, and behavioral supports to move on, and they need all the systems to come together."
She said the students who come to Arise for ninth grade are far behind and struggling and need extra help that her small, specialized school provides.
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Inquirer staff writer Martha Woodall contributed to this article.