Low-income school districts are most likely to place students in special education programs for mild and sometimes questionable disabilities, a practice that has swelled the state’s special education population to one of the highest rates in the nation, according to a first-of-a-kind study commissioned by the state.
The study - to be presented at a state Board of Elementary and Secondary Education meeting Monday night - is expected to provoke debate over whether low-income districts are placing students in special education because of legitimate disabilities or because of weak academic programs that cause students to fall behind, or because some teachers want unruly students out of their classrooms.
That low-income districts are more likely to identify special education students debunks a long-held belief in Massachusetts that it is the savvy, well-heeled parents in wealthier districts who have been pushing up special education rates as they demand advantages for their children, such as extra academic support and waivers from time limits on standardized tests.
“The thesis almost universally accepted throughout the state - that wealthy parents are driving this process - is not found at all,’’ said Thomas Hehir, one of the study’s authors, who is a professor at the Harvard University Graduate School of Education and is a former director of the special education office at the US Department of Education.
Hehir said it is reasonable to expect low-income students to be diagnosed with disabilities at higher rates than other students because they are more susceptible to health problems, such as those caused by high exposure to lead or by lack of prenatal care.
But Hehir said the rate at which low-income students are being enrolled in special education under categories that involve some level of subjective interpretation exceeds rates that specialists consider appropriate. The study did not identify reasons for this.
More than 163,000, or 17 percent, of Massachusetts students are enrolled in special education, the second-highest rate in the nation, according to the study. The Bay State comes behind Rhode Island.
Mitchell Chester, the state’s commissioner of elementary and secondary education, ordered the study to find out why so many students enroll in special education and why those students tend to score poorly on standardized exams despite the often-costly interventions they receive.
“My intent is making sure the students who are identified are truly disabled,’’ Chester said, “and that they are getting the highest quality of instruction we can provide for them.’’
The study urges the state to help districts stop the over-identification of low-income students for special education and reduce the practice of teaching special education students in separate classrooms, among other recommendations.
Chester said he intends to discuss the recommendations with the state board, which could eventually vote on implementing some of the measures.
Special education can often be a double-edge sword for students, specialists say.
A student receiving one-on-one support from a physical therapist or classroom aide can blossom academically. But enrollment in special education programs can carry a stigma resulting in low self-esteem, lower expectations from teachers, and isolation from students outside the program.
“Special education is very bureaucratic - [staff] have to do a lot of paperwork,’’ Hehir said. “Is that the most effective way to get help for kids in school? I would say no.
“Special education is not a program for every kid to get help in school. It shouldn’t be. It’s a disability program.’’
To determine whether a student qualifies for special education, a school needs to assess whether his or her disability is impeding learning.
Special education students represent a broad cross-section, including those with Down syndrome, autism, and dyslexia.
The study focused on students with mild and more broadly defined disabilities, such as specific learning disability, or communication or health impairments that can include attention-deficit hyperactivity disorder.
Determining special education eligibility for those students can be more subjective.
Nearly two out of three special education students statewide were in those categories.
And by examining data the state collects on students’ backgrounds, the study found that low-income students were nearly twice as likely to be placed in these more subjective categories than their more affluent peers.
The study also uncovered a prevalent and troubling practice among low-income districts: Those schools were more likely to teach special education students in separate classrooms, often to a student’s detriment. An analysis of MCAS results, conducted by the authors, revealed that students in separate classrooms scored lower than their counterparts in regular classrooms.
Some of the study’s findings echoed a report the Boston public schools commissioned three years ago on its system, which found that the district taught too many special education students in separate settings and might have been over-identifying students for special education.
The findings led to an overhaul of the system.
“The superintendent [Carol R. Johnson] thinks it’s interesting but not surprising that other districts are encountering the same challenges that we are,’’ said Matthew Wilder, a Boston schools spokesman.
“One of our big goals is to create more opportunities to educate kids in inclusive settings. We are not where we want to be yet, but we are making great progress in that area.’’
About half of Boston’s special education students are taught in classrooms segregated from the general school population for all or part of the day, while special education enrollment has dropped slightly over the past three years, from 20.5 percent to 18.7 percent.
Overall, the state study found that special education students tended to do better on the Massachusetts Comprehensive Assessment System exam in districts where general-education students had high scores - an indication that districts with more academic rigor are better serving their special education students.
The study, however, faulted affluent districts in one area: Even though they had lower overall enrollment rates for special education, they were more likely to refer their small populations of low-income students for special education. The study offered no explanation for that finding.
Tom Scott, executive director of the Massachusetts Association of School Superintendents, said some districts, regardless of wealth, may be over-identifying students under pressure from the state and federal governments to demonstrate that all their students are making academic progress.
“We probably are identifying a number of students who are not keeping up with their peers and may not have a learning disability, but school personnel are feeling the need to give them additional support,’’ Scott said. “Sometimes we unfortunately have few options to fill that need.’’