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A new research review finds inconsistent benefits for students with disabilities who learn alongside general education peers. Credit: Lillian Mongeau/The Hechinger Report

For the past 25 years, U.S. policy has urged schools to keep students with disabilities in the same classrooms with their general education peers unless severe disabilities prevent it. It seems a humane policy not to wall off those with disabilities and keep them apart from society. Who would argue against it?

Schools have embraced inclusion. According to the most recent data from 2020-21 school year, two thirds of the 7 million students with disabilities who receive special education services spent 80 percent or more of their time in traditional classrooms. Separation is less common today; only one out of every eight students with disabilities was taught separately in a special-needs only environment most of the time.  

But a recent international analysis of all the available research on special education inclusion found inconsistent results. Some children thrived while others did very badly in regular classrooms. Overall, students didn’t benefit academically, psychologically or socially from the practice. Math and reading scores, along with psychosocial measures, were no higher for children with disabilities who learned in general education classrooms, on average, compared to children who learned in separate special education classrooms. 

“I was surprised,”said Nina Dalgaard, lead author of the inclusion study for the Campbell Collaboration, a nonprofit organization that reviews research evidence for public policy purposes. “Despite a rather large evidence base, it doesn’t appear that inclusion automatically has positive effects. To the contrary, for some children, it appears that being taught in a segregated setting is actually beneficial.”

Many disability advocates balked at the findings, published in December 2022, on social media. An influential lobbying organization, the National Center for Learning Disabilities, said it continues to believe that inclusion is beneficial for students and that this study will “not change” how the disability community advocates for students. 

“Students with disabilities have a right to learn alongside their peers, and studies have shown that this is beneficial not only for students with disabilities but also for other students in the classroom,” said Lindsay Kubatzky, the organization’s director of policy and advocacy. “Every student is different, and ‘inclusion’ for one student may look different from others. For some, it could be a classroom separate from their peers, but that is rarely the case.”

The Campbell Collaboration study is a meta-analysis, which means it is supposed to sweep up all the best research on a topic and use statistics to tell us where the preponderance of the evidence lies. Dalgaard, a senior researcher at VIVE—The Danish Centre for Social Science Research, initially found over 2,000 studies on special education inclusion. But she threw out 99 percent of them, many of which were quite favorable to inclusion. Most were qualitative studies that described students’ experiences in an inclusion classroom but didn’t rigorously track academic progress. Among those that did monitor math or reading, many simply noted how much students improved in an inclusive setting, but didn’t compare those gains with how students might have otherwise fared in a separate special-needs-only setting. 

Fewer than 100 studies had comparison groups, but still most of those didn’t make the cut because the students in inclusive settings were vastly different from those in separate settings. Special education is a particularly difficult area to study because researchers cannot randomly assign students with disabilities to different treatments. Schools tend to keep children with milder disabilities in a regular classroom and teach only those with the most severe disabilities separately. In comparing how both groups fare, it should be no surprise that students with milder disabilities outperform those with more severe disabilities. But that’s not good evidence that inclusion is better. “It’s a serious, confounding bias,” Dalgaard said.

In the end, Dalgaard was left with only 15 studies where the severity of the disability was somehow noted so that she could compare apples to apples. These 15 studies covered more than 7,000 students, ages six through 16, across nine countries. Four of the studies were conducted in the United States with the others in Europe. 

The disabilities in the studies ranged widely, from the most common ones, such as dyslexia, ADHD, speech impairments and autism, to rarer ones, such as Down syndrome and cerebral palsy. Some students had mild versions; others had more severe forms. I asked Dalgaard if she found clues in the results as to which disabilities were more conducive to inclusion. I was curious if children with severe dyslexia, for example, might benefit from separate instruction with specially trained reading teachers for the first couple of years after diagnosis. 

Dalgaard said there wasn’t enough statistical evidence to untangle when inclusion is most beneficial. But she did notice in the underlying studies that students with autism seem to be better off in a separate setting. For example, their psychosocial scores were higher. But more studies would be needed to confirm this. 

She also noticed that how a school goes about including students with disabilities mattered. In schools that used a co-teaching model, one regular teacher and one trained in special education, students fared better in inclusion classrooms. Again, more research is needed to confirm this statistically. And, even if co-teaching proves to be effective over multiple studies, not every school can afford to hire two teachers for every classroom. It’s particularly cost-prohibitive in middle and high school as teachers specialize in subjects. 

Instead, Dalgaard noted that inclusion is often a cost-cutting practice because schools save money when they no longer run separate classrooms or schools for children with disabilities. “In some cases, children with disabilities no longer had access to the same resources. It’s not supposed to happen this way, but it does in some places,” said Dalgaard. “That is probably why the results of the meta-analysis show that some children actually learn more in segregated settings.”

I was surprised to learn from Dalgaard that no sound meta-analysis has found “clear” benefits for special education inclusion. Indeed, previous meta-analyses have found exactly the same inconsistent or very small positive results, she said. This latest Campbell Collaboration study was commissioned to see if newer research, published from 2000 to September 2021, would move the dial. It did not.

As a nation, we spend an estimated $90 billion a year in federal, state and local taxpayer funds on educating children with disabilities. We ought to know more about how to best help them learn. 

This story about special education inclusion was produced by The Hechinger Report, a nonprofit, independent news organization focused on inequality and innovation in education. Sign up for the Hechinger newsletter.

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Letters to the Editor

3 Letters

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  1. re:
    Ref: The effects of inclusion on academic achievement, socioemotional development and wellbeing of children with special educational needs

    Jill Barshay, Hechinger Reports
    cc Dr. Nina Dalgaard

    It is important to conduct periodic meta-analysis of topics related to public policy, funding and other aspects of education.

    I disagree with the reporting by Jill Bashay regarding special education learner inclusion/exclusion.

    The reason for my disagreement is that the referenced study authors report contains the authors’ data collection and meta-analysis conclusions (see below) that valid information for meta-analysis is inadequate. My read of the Dalgaard met-analysis report suggests that the two extremes – full inclusion or full exclusion – of SEN students in the ‘normal’ population may be harmful but is really unknown. Therefore, until more and better research is achieved, some logical blend of inclusion/exclusion can be designed and implemented to achieve learning and social integration objectives. My opinion comes from leading manufacturing ventures that have intentionally accommodated “SEN” adults successfully in ways that give them personal work settings along with collaborative opportunities. The emotional intelligence for diversity, equity and inclusion is, I believe, better achieved by starting in the K-12 system.

    Larry Gebhardt Ph.D., Captain US Navy (Retired)
    Pocatello, Idaho

    Data Collection and Analysis
    The total number of potentially relevant studies constituted 20,183 hits. A total of 94 studies met the inclusion criteria, all were non-randomised studies. The 94 studies analysed data from 19 different countries. Only 15 studies could be used in the data synthesis. Seventy-nine studies could not be used in the data synthesis as they were judged to be of critical risk of bias and, in accordance with the protocol, were excluded from the meta-analysis on the basis that they would be more likely to mislead than inform. The 15 studies came from nine different countries. Separate meta-analyses were conducted on conceptually distinct outcomes. All analyses were inverse variance weighted using random effects statistical models. Sensitivity analyses were performed to evaluate the robustness of pooled effect sizes across components of risk of bias.

    Authors’ Conclusions
    The overall methodological quality of the included studies was low, and no experimental studies in which children were randomly assigned to intervention and control conditions were found. The 15 studies, which could be used in the data synthesis, were all, except for one, judged to be in serious risk of bias. Results of the meta-analyses do not suggest on average any sizeable positive or negative effects of inclusion on children’s academic achievement as measured by language, literacy, and math outcomes or on the overall psychosocial adjustment of children. The average point estimates favoured inclusion, though small and not statistically significant, heterogeneity was present in all analyses, and there was inconsistency in direction and magnitude of the effect sizes. This finding is similar to the results of previous meta-analyses, which include studies published before 2000, and thus although the number of studies in the current meta-analyses is limited, it can be concluded that it is very unlikely that inclusion in general increases or decreases learning and psychosocial adjustment in children with special needs. Future research should explore the effects of different kinds of inclusive education for children with different kinds of special needs, to expand the knowledge base on what works for whom.

  2. Of course inclusion, just in general, doesn’t increase outcomes. Just like exclusion, just in general, doesn’t help anyone. So many other things have to be true. What the kids and adults are actually doing when they are being ‘included,’ matters the most. Is there one general education teacher with 25 kids and kids with disabilities are just in class receiving whole group instruction without any targeted supports? Is there a strong co-teaching model led by two content experts with most time spent in small groups? Is the special educator a content expert? If you think about what is true about a self-contained classroom that would, arguably, be better for a student, those things can be replicated within a general education setting. As a school leader, professor, former self-contained, and inclusion teacher, there is no arguing with the notion that a non-verbal student with autism is NOT categorically better off in an autism classroom than in an inclusion classroom with strong language models. The structure of the classroom and the roles of adults have to be strategically designed so that kids benefit from any classroom structure, inclusion or otherwise. I have trained hundreds of school leaders all across the country and have learned that most schools don’t know how to do inclusion well. Let’s talk about that.

  3. I am in total agreement with Tony Barton’s comment. Jill Barshay’s article reinforced what we know: that the right set-up plays a critical role in the outcome. Therefore, since there are so few properly conducted studies, we must focus our attention to ensure that our students with disabilities are all in settings that are conducive to progress in all domains- academically, psychologically and socially. Ensuring all our educators are properly trained is the first step.
    I have also found that I will create the learning environment for each struggling student based on the current conditions – and include each student’s personality traits as part of the assessment done to determine where the student will truly feel best and progress most.
    This is similar to a general statement regarding pain. One can never compare his pain to another since pain is physiological and cannot be measured via comparison. Since the personality and individual abilities of the student, teacher, assistant and special educator all will impact the student’s outcome- it is hard to measure and determine where success is most feasible without being aware of all variables. I agree that most schools don’t know how to do inclusion well- or don’t have the staff to properly support it.
    This article is great in raising our collective awareness of why the Campbell Study couldn’t be more targeted and concise with its results and what we can do to support our students best.

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