A while ago, I posted this meta-analysis on Universal Design for Learning. This Campbel review by Dalgaard from December last year looks at the effect of inclusive education versus a more traditional special education approach to learning. The results are more nuanced, or better: it seems to depend:

Results of the meta-analyses do not suggest any consistent 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 studies in the analysis demonstrated a wide range of both large positive and large negative effect sizes; and although the average effect sizes did favour inclusion, they were small and none were statistically significant.

One could argue that more learning isn’t really the point of inclusive education, but rather being inclusive itself. Still, that the average hides large positive and negative effects should make us worry. While the large positive effects are great miracles, the large negative effects are often personal dramas. But also on the part of inclusive education, the results seem to be mixed:

…the findings from this review suggest that while some children with special needs may benefit from inclusive educational placement, other children may benefit from traditional special education in a segregated setting. Unfortunately, it was not possible to explore the effects of different kinds of inclusive education for different kinds of children with special needs.

But the biggest warning is in line with the UDL-meta-analysis:

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.

As somebody who thinks inclusion is something more than worthwhile, I think we should level up the quality of the research.