Dozens of Baltimore classrooms could be staffed by long-term substitutes when school begins, a plan drawing concern particularly because special-education students — who often struggle the most academically — could be the largest group affected.

System leaders and local advocates are expressing reservations about the plan to fill some of the system’s 190 teacher vacancies.

David Stone, vice chair of the city school board, said poor performance on state tests by special-education students this year shows that stability in their classrooms is important.

Only 18 percent of special-education students demonstrated proficiency in eighth-grade reading on the most recent Maryland School Assessments, to take one example.

“We saw those test scores recently, and they were abysmal,” Stone said. “Certainly having an instructor is a big part of that.”

Advocates said long-term substitutes may not be as qualified to meet the demands of the students as experienced, certified special educators.

Special-education students have individualized education plans, or IEPs, that schools are required by law to follow. The city school system was mired in a federal lawsuit for nearly three decades over failing to provide services under these plans.

Leslie Margolis, managing attorney at the Maryland Disability Law Center, which represented the plaintiffs in the lawsuit, said the use of long-term substitutes has long been a point of contention.

“There have been a number of issues over the years with the use of long-term subs, where IEPs were not being met,” Margolis said. “It raises a concern that it could potentially be a problem based on how they staff and what the needs of the students are.”

Lisa Grillo, the school system’s chief human capital officer, said the district would look to staff special-education classrooms with substitutes who have experience working with those students and have shown themselves to be highly effective in the classroom.

To work in special education, a long-term substitute must have a degree or state certificate in the subject or in special education, or complete a school system training course.

As of last week, the district still needed about 50 special educators for the coming school year. Teachers return to work this week; the first day of school is Aug. 25.

For years, the city kept excess teachers — teachers on the payroll without permanent assignments. But there has been an effort in recent years to purge that pool.

Grillo said the smaller number of excess teachers has forced the system to recruit more candidates. In subjects such as math and science, in which the city also has a high number of vacancies, the system is competing with neighboring school districts, she said.

Teachers recruited from the Philippines also filled areas such as science, math and special education. But in recent years, the district has had to cut back on the number of teachers whose visas it could sponsor.

The number of vacancies is less than it was at this point last year. But Grillo said the new administration will look to overhaul the way it recruits teachers.

Gregory Thornton, the new schools CEO, took the helm July 1, bringing Grillo with him to lead the long-troubled human capital office. The district had 424 vacancies in early July.

In the future, Grillo said, recruiting teachers will be a “12-month initiative,” rather a seasonal effort starting each spring.

Principals have the autonomy to hire staff, and the school system has not forced principals to hire certain teachers. Officials have pointed to that approach as a reason schools have opened with vacancies in previous years.

Grillo said the district would look at modifying its rules on hiring at the school level to make sure that staffing decisions aren’t being left to the last minute.

“We want to respect and honor principal autonomy,” she said. “But if our goal is to have a certified high-quality teacher on the first day of classes, we have to make sure that all of our practices and systems support that.”

She said the school district will try to cut back on the use of long-term substitutes.

Last year, the district spent $7.1 million on substitutes, salary records show.