Why I Am Against Mixed Ability: Part 2

November 29, 2015

Last weekend, I spoke at the Debating Education event, at Michaela School, opposing mixed ability teaching. Hopefully the video of the event will appear in the next week or so. The following is a rough summary of what I said (i.e. it’s me going back over my notes and reconstructing my argument but nothing like my exact words). Obviously, it is in no way intended as a research article on mixed ability teaching or a summary of the evidence, just an explanation of my views. This is continued from Part 1.


Like a lot of trainee teachers, I was told on my PGCE course that the empirical evidence strongly supported mixed ability. It was a bit of a shock to look at this evidence and see how poor much of it is. A number of studies consist of tiny trials, where two schools (one with ability grouping, one without) are compared and the results of those schools reported back. Or in the case of Jo Boaler’s research, the actual results are ignored and mixed ability is reported to be better regardless. Even when you look at meta-analyses which include small trials like this, the outcome tends to show either virtually no impact, or a negative effect, for mixed ability. One of the few meta-analyses that suggests ability grouping is marginally harmful is Slavin (1990) though this was after including some remarkable outliers that others might well have ignored. Overall, Hattie combined the meta-analyses to find ability grouping to have an effect size of 0.12. Much of the so-called research in this area is little better than propaganda, declaring mixed ability to be right and attempting to shift the burden of evidence to its critics. Slavin, above, springs to mind as an example of this, his meta-analysis declared, a priori, that ability grouping was “anti-democratic” and “anti-egalitarian”. Betts et al (2000) also identified a tendency for research to compare progress for high and low ability sets with entire mixed ability sets (i.e. not just the high or low ability students in that set), and declare that this showed that while high ability students might do better in ability groups, low ability groups did worse. A trivial outcome that results from not comparing like with like. If there is any good research on setting, it is the randomised control trial conducted in Kenya by Duflo et al (2008) and it found a positive effect for ability grouping for students of all abilities.

It is sometimes claimed that ability grouping leads to stigma and labelling, i.e. that students in the bottom set will feel worse about themselves as a result. On the one hand I doubt this, because students are often even more acutely aware of their lack of ability when in the same class as their more able peers. But I would also look at what’s happened in the years since ability grouping became less popular. Far from refusing to identify the highest attainers as better, they have been listed as “gifted and talented”. Rather than ceasing to single out low attainers we now have 1 in five children identified as having SEN, often for nothing more than low academic attainment. This is not removing stigma; it’s ensuring that differences that could have been accommodated within the curriculum are now seen as problems that require more labelling and more treating students as fundamentally different.

Finally, it is often claimed that if education is focussed on equity, then that would give us reason to avoid ability grouping. It is claimed that it enables us to help the students who are most behind to make the most progress. But if we do want to help the least able, ability grouping favours that aim and mixed ability hinders . With ability grouping, schools can make conscious decisions to make the bottom sets smaller, or provide them with more resources, if they so choose. Mixed ability actually hinders support for the least able as they are split between different classes and dependent on different teachers. If we want to help the weakest, then ability grouping helps us meet their needs. You wouldn’t send everyone to hospital in order to avoid letting the ill and injured feel excluded. You wouldn’t send everyone to court or to prison, so that those who are actually accused or convicted of a crime can avoid stigma. If you set up a food bank, you would put it where the hungry could get to it, you wouldn’t just go from door to door in the nearest street giving everybody a sandwich. You don’t meet needs by ignoring them. Identifying what students need, and providing it, is the aim and ability grouping helps us achieve that.



  1. […] I am against mixed ability:Part 1 and Part 2 by Andrew […]

  2. How about mixed ability but the teacher actually differentiating instruction??

    • It’s rarely possible to differentiate instruction in a class if you only have one teacher. Most differentiation is by outcome or by resources.

      • Do you have a post on how differentiation is pretty much impossible? If not, it would be a good topic!

  3. Yes – like you, I’m skeptical of the research and I tend to agree with you on empirical and instinctive grounds. I’m torn now, between what seems to make sense and the supposed evidence. I’d like to see much more robust research, where ability groupings are along modern principles of providing the appropriate level of instruction rather than dumping pupils into a ‘bucket’ set.

  4. Reblogged this on The Echo Chamber.

  5. In the K-8 school I attended, grouping was flexible. If you did well in your classes, you could be advanced to a higher ability group. So “ability” was based on performance, not just IQ or similar measures. See: http://www.theatlantic.com/national/archive/2013/03/lets-go-back-to-grouping-students-by-ability/274362/

  6. […] The posts I wrote about it can be found here and here. […]

  7. I have now had a chance to read part 2 (thanks for responding to my comment on part 1), however, I am still struggling to understand why you are against mixed ability teaching.

    Hattie’s effect size of 0.12 for ability groups, is very small demonstrating ability grouping has little overall benefit, which would fit with the research I have read. Interestingly, he found a more meaningful effect size of 0.61 for ‘not labelling pupils’ and 0.49 for ‘small group learning’. This fits with the my comment on part 1, that the best approach is mixed ability classes (which does not label students) with flexible in class groupings and small group work with a high performing teacher on occasions for pupils at either end of the ability scale. However, the effect size table is nearly 6 years out of date so new research may have altered these effect sizes (either up or down).

    I had a quick look at the paper published in Kenya, which found positive evidence for ability grouping. However, as this paper points out Kenya is a developing country and therefore comparing the education system to developed countries is not helpful. One of the reasons for caution is, for example, in the schools that used tracking (ability setting) teachers were more likely to turn up and teach.

    In summary, Hattie’s meta-analysis did not find strong evidence for ability setting and the only paper to show a positive effect is in an education system that is not comparable to the UK or US.

    If you have more compelling evidence please do share it – I want to make sure the advice I give to schools is based on the best evidence available, but I have yet to be convinced that I should be advising schools to ability set.

    Link To Hatties’s 2009 Effect size table: http://visible-learning.org/hattie-ranking-influences-effect-sizes-learning-achievement/

    • Let me put it the other way round then. The effect size for mixed ability is -0.12.

      Why use mixed ability?

      • That effect size doesn’t tell us anything about mixed ability. All it shows it that you sort pupils by ability then the effect size is very small. This would make sense as research shows some benefit to high ability pupils, no benefit either way to mid range and a negative benefit for low ability (hence a small effect size overall). Hattie has not directly given an effect size for mixed ability (you can’t just flip the number around otherwise you would get results such as large group teaching group yields a negative effect of -0.49). The closest effect size to mixed ability is for ‘not labelling pupils’ (0.61) as when you put children into ability groups you by consequence label them.

        • The point is that if you dismiss ability grouping for having a small effect size you can dismiss mixed ability for the same reason. And, given that the effect size was based on direct comparisons, yes you can flip it, and I would argue that you should as many of the researchers considered mixed ability, not setting, to be the intervention they were testing.

          Oh, and I addressed the point about labelling earlier. I think setting decreases the need to label, as it allows us to deal with extremes of ability within the curriculum, rather than labelling and providing extra help on the basis of a label.

          That said, it is pointless looking for effect sizes for things that are like mixed ability but not actually mixed ability. If we can do that then why can’t we look at the effect sizes for accelerated sets? They are hugely positive and do require setting.

  8. I don’t disagree that mixed ability teaching may not have large overall effect size. As I have said in my previous comment. It is not one or the other, having mixed ability classes, with within group ability setting that is flexible (with additional pull out small groups) seems to be the best for all students. Whereas, we know from many research studies that ability setting is detrimental to lower ability students. The Education Endowment Foundation based on its meta-analysis finds a small negative effect of -.09 for ability setting on low ability pupils. This equates to a loss of 1- 2 months of progress a year for low ability learners when compared to similar learners in mixed ability groups.

    Why have any set up that is going to particular disadvantage weaker learners? It makes no sense for you to advocate this. You may have experienced ‘bad’ mixed ability teaching, but that doesn’t make the case for separating students by ability or intelligence (as if this is fixed and unchanging).

    I can see that whatever evidence is out there, you will not move from your position. I am open to new evidence – but as yet, I have not come across any evidence that makes a compelling case for ability setting, However, I have found lots of evidence that makes the case for mixed ability groups and small group tuition (where those of similar ability are given specific and focused support by a high performing teacher).

    There is also a great deal of ‘soft’ evidence of students feelings about ability setting and how it makes them feel bad, pressured, not individual e.g. teachers saying things like, ‘you are supposed to be set 1 so this should be easy’.

    So I look forward to any evidence that you find and will always review my position on light of this, but as yet, I am still an advocate of a mix and match approach. It doesn’t have to be one or the other.

    • I think (I can’t be sure as the methodology is pretty unclear) the EEF got its negative effect by including a meta-analysis of within class grouping that had a negative effect. If I’m correct, the very method you propose as a compromise between ability grouping and mixed ability, is actually the only type of ability grouping that does have a negative effect.

  9. Although my thesis is not directly measuring the effect of ability setting v mixed ability – one of the schools I am conducting research in does ability set in Yr 6 but not Yr 5. I am measuring ‘theory of maths intelligence’ (self report) and effort grades (teacher generated) both pre and post the intervention (use of behaviour specific praise statements). It will be interesting to see if the mean score of ‘theory of maths intelligence’ is higher or lower between the year groups. I will analyse this when I have finished data collection and let you know what I find.

  10. […] Why I Am Against Mixed Ability Part 2 (Andrew Old) […]

  11. […] Against Mixed Ability: Part 2”. [blog post] Scenes From The Battleground. Available at:  https://teachingbattleground.wordpress.com/2015/11/29/why-i-am-against-mixed-ability-part-2/ [Accessed 26 May 2018].Michaela Community School, 2015. Mixed ability works. [online video] […]

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