The Class Size Myths – Which do you believe?

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Over the Australian Summer I finally decided to read John Hattie’s Visible Learning for Teachers.True False

Hattie’s theories on education are backed up by countless research papers and evidence.

In the never-ending quest to improve teaching (and teachers) Hattie is as revered by politicians and system leaders around the world as he is viewed with suspicion by front-line teachers.

His most controversial assertion is that reducing class size is a waste of time and money. His research proves having fewer kids in class has little impact on teaching and learning.

And don’t the politicians love that!

Bigger Classes = Fewer Teachers = Less money needed for education – Take that Gonski!

In Queensland, the state government has moved to remove the maximum class size limit, presumably confident of a Coalition victory in the September Federal Election, given that Shadow Education Spokesman Christopher Pyne is on record as saying that class sizes have little impact on teaching.

But here’s the thing… each of the interventions that Hattie studied, were done so in isolation.

Does reducing class size in and of itself improve teaching? Is it the silver bullet? 

Of course not. A crap lesson in front of 40 kids will still be a crap lesson in front of 20. Hattie himself makes the point that looking at class sizes in isolation showed that some teachers didn’t change their methods regardless of the number of kids in front of them.

But when you look at Hattie’s list of interventions that he claims DO have a great impact then things really start to get interesting with regard to class size.

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A teacher’s ability to implement any one or all of these interventions is impacted on by the amount of kids they have in front of them. Anyone who says different has no understanding of teaching, or is clinging to this ideology because it’s the theory du jour and is probably helping them climb the international speaking ladder.

So when politicians say that they won’t be supporting a reduction in class size, what they are actually saying is that they do not support the concepts of developing high expectations for each student, providing quality feedback, improving teacher-student relationships, implementing quality vocabulary or comprehension programs. What politicians are saying is “We’re not particularly interested in improving teaching and learning in our schools. It’s just a little bit too expensive.”

This myth of class-size being irrelevant has permeated into the education debate in many countries like the UK and US. Although, interestingly not Finland where the government agreed to reduce class size, and now the average class size is around 20 kids, with science lessons capped at 16. Sixteen!!

I’m not dismissing Hattie’s work out of hand as I agree with every single one of his “High Influence” interventions for improving teaching & learning – it’s just that having smaller class sizes is essential in order to enable teachers to implement these interventions.

You can read more about the mathematics behind effect size here…

23 Comments on “The Class Size Myths – Which do you believe?

  1. I teach in the U.S… Class size matters, but it’s also the teacher’s classroom management skills that can determine a lot of things. In larger classes, discipline problems tend to arise. If a teacher cannot handle those daily occurrences or nip them in the bud to deliver instruction, it becomes problematic for learning to occur. Again, class sizes matters, but effective classroom management plays a bigger part in the whole equation. That being said, I prefer smaller classes, but I’ve had classes pushed to the limits in regards to numbers – it’s just a bigger challenge #noWorries

    • Thanks for stopping by! I completely agree that classroom management is a key ingredient… I’m just also of the opinion that the challenge of classroom management increases as does the class size.

  2. Hattie noted that as class size decreased, the amount of time the teacher spent talking increased. Surface Vs Deep learning. I just wonder if it was the novelty of students just listening! give me a class under 25 anytime.

    • I like being able to give more individual attention to students and more feedback. More pupils equals less time to be able to do both these things. Big classes can mean I can’t get around to everyone enough to help out with problems they may have. I absolutely disagree that class sizes have zero effect!

    • @Jason: 😀 I think you might be on to something here!
      @Viviene: And that Viviene is because you are a teacher – something many experts are not!
      Cheers for stopping by!

  3. Hattie argues that feedback is (one of) the most important factor(s) when it comes to improving student achievement. In large classes, it’s much more difficult to give the same level of feedback as smaller class sizes, both in terms of “instant” feedback (a smile, a comment) during lesson time or extended feedback (marking) outside of face-to-face time. In the high school context, especially in the “elective subjects,” this is especially problematic. I once had 600 students across 3 schools (4 classes of 30 students per day). Writing that many reports, let alone giving extended feedback on written work, was very challenging… Sure, I was able to repeat lessons (hence reducing prep time) but I didn’t *know* the students and I wasn’t able to provide effective feedback to them nor plan according to the feedback they gave me.

    • And it’s details like this that proponents of the “Class Size Doesn’t Matter” argument seem to miss time and time again.
      Thanks for commenting Penny, I appreciate it.

  4. It makes sense that the smaller the class size the more time a teacher is able to focus on each individual student. In high school I think class size is very important since a teacher may only see an individual student for only 3x 70minute lessons. Fostering student/teacher relationships is KEY to learning imo and this is made difficult as the class size increases.

    • Thanks for the comment, I agree that relationships are at the heart of learning… Even Hattie has it as one of his “High Influencers” which makes his class size argument all the more confusing.

  5. If you teach in a “traditional sense”, class size doesn’t matter. The workload is more for a teacher in terms of marking, but there will no be impact in the learning of students. If I lecture in front of 15 does it matter if I lecture in front of 30?

    That being said, if they are looking at changing the dynamic of the classroom in our classrooms where it is (and should be) more student focused, then class size would matter. How much personal attention can I give to 15 students as opposed to 35? Did they look at the teaching that many politicians say they would prefer?

    I wrote about this here:

    Thanks for your post!

    • Thanks for stopping by George – I appreciate it, and thanks for the link too!
      I think you ask a pertinent question – What kind of teaching do politicians want?
      I think if we also consider the clamouring around the Kahn Academy, I’m beginning to think that ed reform might boil down to herding hundreds of kids into big halls to watch youtube clipped streamed from the US. 😉
      Cheers again,

  6. I teach in a private school that limits class size to 12 students, grades K-8. I currently have ten students in my class. In previous schools, I’ve had up to 36 students in one room. I no longer think about what will be most “efficient” (read here: convenient for me) activity to teach, guide, and assess. The smaller class size helps me not only give individual attention to ALL of my students, but provides them the freedom to take on projects that are time-consuming. Many of the assessment tools, assignments, and other learning activities in schools with large class sizes are produced for the convenience of the teacher/educator who must find a timely way to provide feedback. I don’t have that problem anymore.

    The benefits of smaller class sizes are numerous, and that’s why, unfortunately, you see them in mostly private schools. Public schools’ priorities tend to center more around cost efficiency than what is best for students.

    • Thanks for stopping by Michelle… indeed Hattie couches his whole argument in the “what’s the best bang for buck?” flavour.
      Obviously more teachers = more money which is why pollies love the fact Hattie says this isn’t the answer. The views being expressed here and on Twitter in response to this article suggest otherwise.
      Thanks again,

  7. If you have ever visited Exeter Academy in New Hampshire, one of the most elite of the American independent schools, class size is often limited to 12. This is how many students can sit around a “Harkness table” (oval and oak). This is based on the Socratic method which I happen to believe is very important. I can not imagine that even Hatie saying that class size has no impact will convince those folks to expand beyond the physical limits of the Harkness table.

    • Alan,
      I really appreciate you taking the time to comment on my little blog! I enjoy following your work and thoughts.
      12 = Educational Utopia?
      I can just imagine the pollies reading this comment immediately calculating the cost of Oak tables! 🙂
      Hope to catch up with you when you’re in Australia later this year?
      All the best

  8. Interesting points. As you alluded to in your blog post, a poor lesson is still poor in front of 40 or 20 students. In the same way, if we reduce average class sizes to 16, we need to embed effective and ongoing PD so Hattie’s list of high influences are truly implemented and ongoing in classrooms. Great food for thought!

    Steve Guditus

  9. As a parent, I would prefer my children to be in a smaller class size. I would like them to be noticed, cherished and challenged. I would like them to strive towards better. I would like them to be able to experiment, fail, try and draft again. I would love the teacher to know them by name and what makes them smile. All this takes TIME. Sensibility and logic tell us that engagement and involvement in learning takes time. Therefore, it seems crazy to think class size does not influence a child’s learning.

    As a teacher, my number one wish? More time…

  10. A great post, many thanks. I fully agree that political reasoning is informed by financial rather than educational thinking. Sadly the ‘easier to measure’ results hold sway and the real art and craft of teaching won’t impress politicians. The education system is driven by group outcomes and individual needs always come second in this culture of league tables.

  11. I would be really interested to hear what readers think Hattie has actually written on this subject, as I think some important points have been missed. Hattie himself is not offering his own theories or research on the class size issue. He simply quotes study after study, and a number of meta-analyses, which have shown that class size – as a single variable – has no measurable effects on student outcomes, unless classes are either bigger or smaller than particular thresholds (from memory the lower threshold is about 10, below which better outcomes are measured). And measuring single variables is in fact what scientists do – control every variable except one, and see if it has an effect. This is the scientific method, and has been the origin of many medical, technological and environmental benefits, simply because it works.

    It is curious to me that whenever I speak to teaching professionals they are all over Hattie’s meta-analytical approach, and use his data to argue their positions about education (as do I), but they reject that same approach when it comes to class size. Those same people then attempt to counter this well-established, voluminous and consistent research with personal anecdotes and interesting hypotheses about why class-size should matter.

    Dan’s hypothesis about small class sizes enhancing the ability to give feedback, build relationships etc, is an interesting hypothesis, and may well prove to be right. But where is the evidence for this? He might be right, and it would be a simple task to empirically evaluate his hypothesis – a preferable option to relying on common-sense or anecdotal ‘evidence’.

    The scientific method – so often shunned by the education profession – dictates that you cannot cherry-pick the evidence – either you reject the evidence (based on, say the methodology, the assumptions, the validity of the measures or whatever), or you accept it. Accepting one finding but rejecting another which was arrived at using the very same methods, is indicative of an unscientific, logical fallacy, and detracts from the independence and credibility of those who do so.

    Finally, I wonder if the teaching profession might have more credibility, and make a more significant contribution to this debate, if it argued about class sizes from an industrial relations perspective (i.e. how it affects teachers’ workload, stress levels etc) rather than trying to fight the unwinnable battle of arguing against the well-established data on student outcomes.

    • I’m a teacher, I’ve read Hattie, and I am far from “all over” his approach. Rather, it looks to me like Hattie is barely competent. He cloaks himself in the mantle of science and demonizes teachers as (basically) hidebound bloodletting quacks, but when I tried last year to understand Hattie’s methods and enlisted a statistician in my efforts, I found deeply questionable practices. Hattie’s own response to my questions was not satisfying. I’m not sure what you mean by “data on student outcomes”, but I don’t see anything that could fit that phrase that looks “well-established” to me.

  12. John Hattie admits that half of the Statistics in Visible Learning are wrong
    by ollieorange2

    At the researchED conference in September 2013, Professor Robert Coe, Professor of Education at Durham University, said that John Hattie’s book, ‘Visible Learning’, is “riddled with errors”. But what are some of those errors?

    The biggest mistake Hattie makes is with the CLE statistic that he uses throughout the book. In ‘Visible Learning, Hattie only uses two statistics, the ‘Effect Size’ and the CLE (neither of which Mathematicians use).

    The CLE is meant to be a probability, yet Hattie has it at values between -49% and 219%. Now a probability can’t be negative or more than 100% as any Year 7 will tell you.

    This was first spotted and pointed out to him by Arne Kare Topphol, an Associate Professor at the University of Volda and his class who sent Hattie an email.

    In his first reply – here , Hattie completely misses the point about probability being negative and claims he actually used a different version of the CLE than the one he actually referenced (by McGraw and Wong). This makes his academic referencing, hmm, the word I’m going to use here is ‘interesting’.

    In his second reply – here , Hattie reluctantly acknowledges that the CLE has in fact been calculated incorrectly throughout the book but brushes it off as no big deal that out of two statistics in the book he has calculated one incorrectly.

    There are several worrying aspects to this –

    Firstly, it took 3 years for the mistake to be noticed, and it’s not as though it’s a subtle statistical error that only a Mathematician would spot, he has probability as negative for goodness sake. Presumably, the entire Educational Research community read the book when it came out and they all completely missed it. So, the question must be asked, who is checking John Hattie’s work? As a Bachelor of Arts is he capable of spotting Mathematical errors himself?

    In Mathematics, new or unproven work is handed over to unbiased judges who go through it with a fine toothcomb before it is considered to have the stamp of approval of the Mathematical community. Who is performing this function for the Educational community?

    Secondly, despite the fact that John Hattie has presumably known about this error since last year there has been no publicity telling people that part of the book is wrong and should not be used. Surely he could have found time between flying round the world to his many Visible Learning conferences to squeeze in a quick announcement.

    As one of the letter writer’s stepfather, a Professor of Statistics said

    “People who don’t know that Probability can’t be negative, shouldn’t write books on Statistics”

    Source: to get the links go to the original blog post

    • Thanks Brendan, this blog is quoted elsewhere on my blog. In response John Hattie agreed to an interview with me.
      Thanks again for stopping by!

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