The city’s efforts to turn around nearly 100 long-struggling schools are likely to run up against enrollment roadblocks, according to an analysis by the city’s education data watchdog group.

Of the 94 schools in the city’s Renewal program, 80 have seen their enrollment dip over the last two school years, and 14 have seen more than one-third of their total enrollment disappear since 2013, the Independent Budget Office’s numbers show. The schools are also serving an outsize share of English language learners, black students, Hispanic students, and students in temporary housing — all of whom typically post lower-than-average test scores and graduation rates.

“To the extent that these schools continue to be avoided by students and families,” the report says, “it is likely that they will consist of higher concentrations of the students most in need.”

The findings mirror the IBO’s annual analyses of schools slated for closure under the Bloomberg administration, which repeatedly found that high-needs students were concentrated in schools with low test scores and graduation rates. The numbers raise old questions about the city’s enrollment policies and new ones about the de Blasio administration’s school-improvement strategy, which doesn’t include mechanisms for reducing the concentration of needy students at Renewal schools.

“Most of the kids who are coming into those schools are already way behind,” said David Bloomfield, an educational leadership professor at Brooklyn College and The CUNY Grad Center. The schools’ low test scores “are not only a result of not getting those kids up to the level of proficiency, but also that they’ve been dealt a hand that puts them behind to begin with,” he said.

Low enrollment poses its own less-discussed challenges. Because school funding is largely determined by enrollment, schools with few students often struggle to offer special-education services or elective classes. Twenty-six of the city’s Renewal schools now enroll fewer than 250 students, and nine enroll fewer than 150, as Chalkbeat reported earlier this month.

Chancellor Carmen Fariña has begun moving to merge a few of the city’s smallest schools (only some of which are in the Renewal program) into larger ones, citing those problems.

Some schools in the city’s Renewal program, especially high schools and those middle schools in competitive school districts, know the enrollment problem well. In March, representatives from high schools with seats left to fill in their ninth-grade classes gave recruitment another try at the city’s second-round high school fair.

One was John Starkey, who started as interim acting principal of Peace and Diversity Academy in the Bronx a few months ago. The high school, which is a part of the city’s turnaround program, now has just over 150 students, and Starkey said he was moving quickly to figure out how to draw new students. The school’s four-year graduation rate was 34 percent last year.

“Enrollment is a big issue for us,” he said. “When your numbers are so low, it affects the money you’re bringing in, what you can do, your programs, your class size.”

As he shook hands with prospective students, Starkey rattled off a half-dozen ideas. He was working to restart a partnership with the Anti-Defamation League, continuing peer mediation training for students, thinking about launching a dual-language program, and trying to find new outlets for students to play basketball and even take Zumba classes.

In addition to more general academic improvements, those offerings would give Peace and Diversity “something to set us apart, help us advertise,” Starkey said. “We want to be a viable program.”

The Academy of Urban Planning, a high school in the Bushwick campus that is also part of the turnaround program, had a less traditional booster: former teacher and softball coach Johnny Alicea, who explained that he had been excessed as enrollment dropped but hoped to return. The school now serves around 260 students.

The city’s highest-profile enrollment decline has happened at the long-struggling Boys and Girls High School in Brooklyn, which has served more than 4,000 students in the past and where the register now shows just over 500 students enrolled. A guide for students said the school still had room to accept nearly 500 students in next fall’s ninth-grade class after the first high school admissions round.

This year, the city also decided not to send students who entered the school system late to Boys and Girls and Automotive High School, another school in the turnaround program. Those “over the counter” students often pose extra challenges but would also have boosted enrollment.

The enrollment problem is an outgrowth of policies introduced by the Bloomberg administration, which closed many of the city’s large, traditional high schools and replaced them with smaller schools. Many of those have thrived, while others found it difficult to recruit students for untested schools with unfamiliar names. Schools can also find it hard to escape what some call an enrollment “death spiral,” when a school’s problems prompt higher-achieving prospective students to enroll elsewhere, compounding a school’s academic troubles.

The closures reduced the number of big high schools serving mostly high-needs students, but the IBO’s numbers show that they are still more concentrated in low-performing schools.

Twenty percent of students at Renewal schools are classified as English language learners, compared to 14 percent of students in other city schools. Fifty-two percent of students at Renewal schools are Hispanic, compared to 40 percent at other schools. The share of special-education students was more similar, with 21 percent classified as having a disability at Renewal schools compared to 18 percent at other schools.

Eleven large, traditional high schools are also in the turnaround program. Together, all 29 Renewal schools serving high school students last year had a four-year graduation rate of just 51.7 percent.

Next year, schools in the Renewal program will have an hour added to the school day and receive money for new after-school programs and more teacher training, according to city officials. Overall budgets will increase by an average of $250,000, money officials have said will help schools better serve English learners, special-education students, “and other young people who need extra help to catch up.”

“Lifting up our schools requires real resources – and that is what we are committed to delivering,” Fariña said in a statement.

Raymond Domanico, the IBO’s director of education research, said that even with those resources, each school’s challenges will remain connected to its ability to attract and retain students.

“If the enrollment continues to decrease, it’s going to be increasingly difficult for the school system to meet the goal of improving its schools,” he said.