I see that it is time for me to a do a tweet thread on how heterogeneous classrooms are actually supported by lots and lots of empirical evidence.

Freedman, S., Delp, V., & Crawford, S. (2005). The focal teacher’s practice of using whole-class instruction combined with individual attention suggests an alternative to using small groups in teaching heterogeneous classrooms.

@joboaler (2006). Students in detracked math achieved more equitable outcomes on tests. Students learned to appreciate the contributions of students from different cultural groups, genders, and attainment levels, a behavior the author terms “relational equity.”

Watanabe, M., Nunes, N., Mebane, S., Scalise, K., & Claesgens, J. (2007). The authors identified 4 key practices in detracked science classrooms that promoted student success: teachers’ beliefs in the malleability of intelligence, inquiry-based learning, teaching study skills...

..., and a strong classroom community in which students feel responsible for their own and other students’ learning.

Boaler, J. & Staples, M. (2008). Among three California high schools implementing mathematics reform, one school implemented heterogeneous classes. Students at this school learned more, had higher levels of math enjoyment, and moved to higher levels of math compared to other 2.

Mayer, A. (2008). "The open-admission International Baccalaureate (IB) program successfully attracted & retained students of color with low SES backgrounds. Author attributes this findings to teachers’ belief in the students’ abilities along with academic and social support...

...mechanisms put in place for these students."

Staples, M. (2008). In analyzing one heterogenous secondary math classroom, the author found four categories that are “critical” in determining the teacher’s role in such a classroom: individual and group accountability, positive sentiment, exchanges between students with ...

...appropriate resources, supporting mathematical inquiry when interacting with groups of students.

Rui, N. (2009). Students in detracked groups performed slightly better academically than their equivalent-ability peers in tracked groups using a fixed effects model. A random effects model also indicated the overall positive effects of detracking.

Schofield, J. W. (2010). International research supports the conclusion that having high-ability/high-achieving schoolmates/classmates is associated with increased achievement, even when holding prior achievement constant.

Burris, C. C., Heubert, J. P., & Levin, H. M. (2016). An accelerated math curriculum in a heterogeneously grouped middle school significantly increased...

...probability of completion of advanced math courses increased and markedly in all groups, including minority students, students of low socioeconomic status, and students at all initial achievement levels.

Card, D., & Giuliano, L. (2016). The authors found that participation in a gifted class leads to significant achievement gains for non-gifted participants, concentrated among black and Hispanic students, who gain 0.5 standard deviation units in fourth grade reading and math.

None of this is to say that there isn't conflicting evidence. There is! But the claim that there's a lack of evidence supporting heterogeneous classrooms is incorrect. Thank you for coming to my literature review.