Ronan Lyons | Personal Website
Ronan Lyons | Personal Website

Teacher performance, class size? Does it even matter?

I came across this excellent review and discussion, by Andrew Leigh of (a great site) of a very interesting paper on education performance (by Brian Byrne of the University of New England), during the summer. Essentially, it uses that treasure trove of the social scientist – identical twins – to attempt to measure the effect of teacher performance on educational outcomes. The entire post and its various links and comments are all worth a read, because the more you read about the subject, the more fascinating it gets.

For example, the paper could easily have been publicised as a measure of the effect of class size but – tell this one to teachers and indeed parents out there – the literature is generally agreed that class size, for most age groups, has no distinguishable impact, hence the authors chose to focus on teacher quality, which after all is much harder to measure, instead.

There’s also a good discussion of what percentages count as not important. For example, even if the bulk of performance is determined by the child, not the teacher or the classroom, an 8% boost to performance is still better than none.

The importance - or not - of class size
The importance - or not - of class size

The ‘everything comes back to Bord Snip Nua’ digression: if indeed class size is not the be-all-and-end-all when it comes to our children’s future, perhaps it could take a slightly lower priority on the pecking order of What Must Not Be Touched in our public expenditure.

  • Kevin Denny ,

    There is something of an obsession with class-size of which both stakeholders and academics are guilty [myself included]. Its partly because it is easy to measure compared to stuff like teacher quality. Even there, one can measure teacher qualifications or pay but that may not be that informative. Ask people was their school good and they will typically not refer to class-size. Or ask people why they like or don’t like English or maths and they say “well my teacher was great/boring…”. That’s suggestive at least.
    The minister has rightly pointed out that the effects are pretty small at the margin although how much of this is political and budgetary expedience I don’t know.
    Forget about the budgetary crisis for the moment. The most important questions in this area are: why are some schools better than others and what can we do about it?
    At the moment there is no chance of addressing these questions in Ireland.

    • Donal O'Brolchain ,

      I am not a teacher nor have I ever been one.
      re. Class size
      Brian Byrne, the author of the study you cite, does make the observation that
      “….., we cannot separate teacher influence from other processes operating at the classroom level. Those processes might include class size (though as I read the literature, within reasonable limits size doesn’t matter much), but includes others as well.”
      On class size, the key question becomes what are the reasonable limits within which size does not matter?
      To go from this unanswered question to almost claim support for what seems to be your position ie class sizes do not matter at all, is a step too far based on the thread you have referred to.

      On my side, I will now go one step further and ask you to consider the following

      1. In terms of management practice, what is the span of control that any one person (eg. supervisor, line manager, SBU manager, CEO) can manage effectively? In other words, how many people can a person with supervisory or managerial responsibility have report to him/her directly and still be managerially effective? I suggest that direct reports to CEOs of any size of organisation, private or public, is rarely greater than 10.

      2. If so, we are talking about 10 mature consenting adults, who have been chosen for the particular roles and who have worked to attain them.

      3. Compare and contrast this with educating children, who must attend school and where teachers have limited influence on the composition of the class into which up 30-35 immature, people-in-a-formative mode are placed. This is more than three times what managers in well-run organisations have report to them.

      4. When I have asked about this, I have formed the view that a class size of no greater than 20 seems optimum. In short, there seems to be a noticeable difference between the measured performance children from classes greater than 20 and not much difference where class sizes are below 20.

      From reading your post, I think you are taking the “data” published in the thread you link to, with a excess of enthusiasm for what I must now conclude is a prejudice against looking at the class size issue.

      Sometimes I get the impression is that “What must not be touched” is what economists think is the position. Economists are no doubt intelligent, numerate and questioning. They often also lack experience in the operational detail and practice of things they poke into.

      • kevin denny ,

        Well, Donal, the academics who do this research, like me, are almost all teaching in universities. So I guess they would have more operational experience than someone who has never been a teacher. Like yourself.
        I am curious to know how the “no greater than 20” is arrived at though.Says who? Not the research anyway. Just comparing the average performance of classes above and below 20 is not informative about the causal relationship between class size and performance. If only it were so easy.
        Its curious how someone who raises the presence of research on a topic questioning the popular wisdom is accused of prejudice against looking at that particular topic. I don’t get that.

        • Donal O'Brolchain ,

          My point is very simple.
          Brian Byrne, author of the original research (which I have not read) comments on the piece to which Ronan referred as follows,
          “…I say “and sometimes less” because, as Andrew points out, we cannot separate teacher influence from other processes operating at the classroom level. Those processes might include class size (though as I read the literature, within reasonable limits size doesn’t matter much), but includes others as well. Herb Marsh, now at Oxford, and others, have identified “classroom climate,” which is independent of the teacher, as influential.”

          What I want to know is what are the reasonable limits within which class size does not matter.

          I would appreciate some references to what the current conventional wisdom is on this issue, based on whatever research you can refer me to.

          I did have a reference for my statement of “no greater than 20” which I cannot find at present. Hence my request for further information.

          That said, I still think it a jump to go from Brian Byrne’s careful comment about the effect of class sizes to Ronan’s statement that there is general agreement “that class size, for most age groups, has no distinguishable impact” Like yourself, I ask “Says who?”

          IMO there is bound to be a difference in the “operational experience” of teaching third level students (eg. history, English, maths, economics, physics, chemistry) and that of teaching a class of ~30 of 4-12 year olds the three Rs + lots of other material or ~25 teen-agers compulsory maths, English Irish and whatever other subjects are needed for state examination purposes.

          • Pelotudo ,

            I am an English language teacher in Spain. I teach adults, teenagers and children. My largest class of chidren is fifteen.I find this to be the most reasonable number of students to have in a class and language learning research has shown it to be the maximum number possible for effective learning. I have been taught the various methodolgies necessary to teach effectively (but I still have a lot to learn) as have any qualified teachers. This is not my point. What my point is… is that you can have all the academic qualifications and methodolgy necessary to teach effectively but if you cannot control the classroom you cannot teach effectively. So for example,you can have twenty adults in a room. They are paying for the class. They are motivated,etc. In this situation the number of students in the classroom is irrelevant. On the other hand, a group of chidren is a completely different situation. Children are easily distracted. They move,fidget,chat,etc. The more students there are in the class the more difficult it is to control them. If you cannot control or maintain discipline then all the teaching methodolgies in the world become useless.
            Also,to put things in perspective there are more restrictions on how teachers can discipline unruly students. When I attended school I had a healthy respect/fear of my teachers.
            To say that class size is irrelevant is wrong.Maybe if you have a group of 30 angels, yes, but thats virtually impossible.

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