A screenshot from the state's proposed enrollment targets calculator. It shows the range of target enrollments for a school enrolling 150 students in Brooklyn's District 15.

The state is preparing to take a step forward in implementing a two-year-old clause in its charter school law that requires the schools to serve their fair share of high-needs students.

When legislators revised the charter school law in 2010, their main objective was to increase the number of charters allowed. But they also added a requirement that charter schools enroll “comparable” numbers of students with disabilities and English language learners, populations that the schools typically under-enroll.

What comparability would mean has never been clear — until now. Last week, the state unveiled a proposed methodology for calculating enrollment targets, and it intends to finalize the algorithm at next month’s meeting of SUNY’s Board of Trustees, which oversees charter schools.

The targets would vary from school to school and be determined based on the overall ratio of high-needs students in each district. The proposal includes a calculator that determines enrollment targets for any school based on its location, the grades it serves, and the size of its student body.

Under the proposed methodology, a charter school with 400 students in grades five through eight in Upper Manhattan’s District 6, for example, would have to enroll 98 percent students who are eligible for free or reduced-price lunch, 15 percent students with disabilities, and 44 percent ELLs. In District 2, which has more affluent families and fewer immigrants, a similar school would be expected to enroll 64 percent poor students and 13.4 percent ELLs. But it would still need to have 15 percent of students with special needs.

Some charter schools already meet and exceed their enrollment targets. But many others fall far short, as a charter sector self-assessment published last month indicated. The report found that 80 percent of charter schools enroll a lower proportion of poor students than their district.

Under the law, repeated failure to meet the enrollment targets could result in a school losing its right to operate. But more immediately, charter schools that don’t meet their enrollment targets will be expected to show a “good faith” effort to boost their numbers, according to Cynthia Proctor, a spokeswoman for SUNY’s Charter Schools Institute.

“Once the methodology is approved and targets set, part of developing authorizer practice will certainly be conversations with schools and related guidance on expectations in terms of good faith efforts to meet targets,” Proctor said in an email.

Those efforts are likely to include focusing recruitment efforts on high-needs populations and asking the state for permission to give preference to different groups of high-needs students in their admission lotteries, as some schools have already done.

“Some of the charters may need to change their enrollment procedures to make sure they’re reaching out to those families and places and centers,” said Jacqueline Frey, who runs DREAM Charter School in Harlem.

But Frey added, “From my perspective, this doesn’t change the nature of how we do our business.” The school has more special education students than the targets would require but slightly too few low-income students and ELLs.

Other charter school operators say the targets represent a step forward in addressing ongoing inequities in charter school enrollments but don’t solve the problem.

“It seems like it’s the outcome we all want, but it doesn’t sound like it’s telling us how to get there,” said Morty Ballen, the founder of the Explore Charter Schools network.

Indeed, schools face real challenges around enrolling some high-needs populations. State law requires that they admit students via a lottery and fill their seats, so charter schools cannot simply set aside a portion of seats for high-needs students. Once schools are full, they cannot admit midyear arrivals, who are often immigrants who do not speak English. Plus, schools that help some students shed their ELL or special education designation could be dinged if their portion of high-needs students decreases.

The methodology could still be changed to reflect some of the challenges. The state’s proposal notes, for example, that ELL students are not evenly distributed within school districts, but instead tend to concentrate in certain neighborhood pockets, so the methodology might generate targets that are unreasonably high or low for schools.

The targets are only for charter schools, but their creation is causing the state to look at enrollment trends in district schools, too. Together, the scrutiny can only be good for students, said James Merriman, executive director of the New York City Charter School Center.

“We support efforts to improve transparency around special education and student enrollment in both charter schools and district schools with the end goal of improving achievement for all kids,” he said.

SUNY’s Charter Schools Institute is holding a webinar May 18 to detail the proposed target methodology and will accept comments about it until May 29.

“We hope that one of the realizations that emerges from the extensive process followed to bring us to the point where we are now is that this is complex work,” Proctor said.