What do teachers need to know? – Part 1 – Subject Content Knowledge

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This is the first in a series of posts on what teachers should know (I tried to write one but it got too long).  The posts will cover:

If you want to skip to some practical advice, scroll down. 

If you could improve one aspect of your knowledge as a teacher, what would it be?  I’m guessing you might choose subject knowledge and I would’ve too until reading one study and following the references turned up some unexpected (and some expected) results.

It’s often surprising how apparently revolutionary ideas aren’t revolutionary at all.  The move from a generic understanding of pedagogy to one inextricably linked to the curriculum feels revolutionary.  But Lee Shulman (1986) was making the case for content knowledge and its ties to pedagogy in the mid-eighties, calling it ‘The Missing Paradigm’ of teacher education.  Shulman’s categorisation of teacher knowledge as subject matter content knowledge, pedagogical content knowledge and curricular knowledge is one source for the recent Great Teaching Toolkit (2020) and its ‘Understanding the Content’ strand.  His writing seems prescient, sharing our current concerns about curriculum and subject knowledge, whilst he, as we might, reacts against training programmes apparently devoid of content knowledge.

Shulman’s categories of teacher knowledge, alongside some more recent research, can provide a roadmap as well as potential pitfalls, for individual teachers or leaders as they seek to answer the question – What do teachers need to know to be effective? 

Subject Content Knowledge

To Shulman, Subject Content Knowledge is the ‘amount and organisation of knowledge’ teachers have about their subject; this knowledge requires understanding of the ‘substantive and syntactic structures’ of the subject area.  Substantive structures are the concepts, principles and, ultimately, facts of any given subject.  Syntactic structures are those which define ‘which truth or falsehood, validity or invalidity are established’.  This knowledge sits between a university level understanding of a subject and the student who is encountering the curriculum.  With this in mind, Baumert and Kunter (2013) point out that maths teachers’ required knowledge for teaching is not the university level maths they may have studied but the knowledge ‘behind the institutionalized curriculum’.  That distinct teacher held, curriculum driven syntactic knowledge is important because it highlights there is a distinction between this knowledge teachers have and simply being a subject expert.

This is not just theoretical; there is research into the impact of teacher subject knowledge on student achievement.  One area looks at teacher qualifications (or other assessments of teacher knowledge) and how they predict student achievement.  Another looks at subject knowledge CPD interventions and how they affect student outcomes.

As Harris and Sass (2007) found, investigations showed that university level qualifications, whilst perhaps poor proxies for teacher knowledge, are no great indicator of teacher quality and in some cases higher level qualifications associate with poorer attainment of students. As the Great Teaching Toolkit points out, teachers need ‘theoretical knowledge of the domain of learning’.  In this way, an English teacher’s knowledge of grammar isn’t necessarily just simplified and then taught as the curriculum but it will certainly inform the teaching of writing.  A good writer isn’t necessarily a good teacher of writing; the teacher needs to understand the foundations of good writing.

That better content knowledge in and of itself leads to better teaching or better outcomes is not a given.  Will reading a book about grammar improve an English teacher’s impact?  Will studying in subject specific courses or for postgraduate degrees?  The answer to these questions is not no but it is also far from yes.  Baumert et al (2010) explain that ‘few empirical studies to date have assessed the various components of teachers’ knowledge directly and used them to predict instructional quality and student outcomes’.  In fact, in a study of maths teachers in Germany, Baumert and co found that ‘higher levels of [content knowledge] have no direct impact… on the potential for cognitive activation… that teachers are able to provide when learning difficulties occur’.  In contrast, Hill, et al (2005) did see ‘content knowledge’ as a ‘significant predictor of student gains’ in primary maths but before we get too excited about this, the content knowledge required was not of a high or academic level; the study suggests the impact of content knowledge professional development could be high but mainly on teachers in the lowest third in assessments of this knowledge.  Teachers need content knowledge mainly when they really don’t have it.

To be clear here, we’re discussing a pure kind of knowledge of the subject being taught, where continual development will see varied or diminishing returns.  A different kind of knowledge, pedagogical content knowledge, as I will show, is very important.

Lawrence Stenhouse said that there is ‘no curriculum development without teacher development’.  As curriculum changes, there is likely a need for more focused content knowledge development.  There is quite a lot of evidence that a strong knowledge-focused curriculum will have an impact on student outcomes and so there is a tension between developing that curriculum, which will require content knowledge, and purely developing content knowledge.  If we believe, as seems sensible, that work on the curriculum is never done, then we may decide to set aside regular time to develop it or work on how it is implemented.  This may involve subject knowledge development but, to have an impact, it will go well beyond that into the careful planning and sequencing of knowledge.  Of course, schools may also decide that the distinctness of subjects and subject expertise sit within their values and therefore time should be devoted to them.


For Leaders

  • Pure Content Knowledge CPD is unlikely to be effective at improving teaching.

Subject conferences, courses and reading are potentially useful, particularly when a member of staff has limited knowledge or new curriculum resources are being introduced or developed.  Content knowledge CPD is likely to be limited in long-term impact for a couple of reasons: it is difficult to direct well and, whilst it won’t have no impact, it will see diminishing returns.

It feels nice as a leader to give development time over to departments and subjects.  This is not necessarily a bad thing; there are conditions, which I will discuss in the next post, where developing specific kinds of subject knowledge can be incredibly effective.  Recently, I’ve heard people claim that reading an article or book about your subject or a similar activity is the most effective kind of CPD you can do.  There may be all kinds of times when these activities are necessary and important but it is not possible to argue from evidence that these are the best CPD activities.

  • Content Knowledge CPD is still important for non-specialists.

The research suggests that non-specialists or those with limited knowledge can see improvements in impact with growing knowledge.  These should be targeted at those theoretical areas staff will need to develop the pedagogical content knowledge necessary to teach the curriculum.

  • Qualifications don’t effectively predict subject expertise for teaching.

We could add on their own here because there are some instances where higher qualifications do correlate with success and it would also be absurd to look for candidates with poorer qualifications in response to this.  Hill et al (2005) argue that ‘direct measures of teachers content knowledge for teaching trumps proxy measures such as courses taken’.  Focusing too keenly on qualifications ignores what needs to be done with those qualifications, and the knowledge attached to them, to make them useful to a teacher.  In the mentioned study, those investigating created their own assessment of teacher content knowledge rather than using qualifications.

I once interviewed an English teacher with a Masters in Literature and a dissertation on Macbeth for a temporary post. I was thrilled and the person was appointed but this person was terrible.  They weren’t terrible because of their subject knowledge but were in spite of that knowledge.

For Teachers

  • Develop theoretical knowledge where you need it

If you’re looking for a way to develop, it might be useful to focus on those areas where theoretical knowledge underpinning what you’re teaching is weaker.  English teachers who are literature specialists often lack confidence in teaching writing in general and grammar in particular because their theoretical knowledge is lacking.  I recently watched an excellent LitDrive video on the Porter in Macbeth.  I lacked confidence in teaching the Porter and the video certainly helped with this.  But, in a subject where the possibilities for this kind of development are pretty much infinite, I don’t have the time to find and plug all those gaps.  Don’t get me wrong, I can work at the ones I’m aware of but we don’t necessarily know where we need to develop and we can’t develop across broad and deep domains quickly.

I love reading about my subject because I love my subject.  If there was time and money available, I’d love to do a literature masters and I’ve heard some suggest this would be good CPD.  Whilst I’d enjoy a masters and postgraduate study might help those leading in subjects and curriculum development, the evidence suggests this won’t have much impact on students in my classes.

  • Beware of over-confidence as subject knowledge grows.

Because the content knowledge is linked to student achievement but only in limited ways, there’s a danger as we develop content knowledge we overestimate how our abilities as a teacher are developing, a kind of subject knowledge Dunning Kruger.   In the next post, I’ll explore how that growth in subject knowledge can lead to and increase outcomes for students.


There are caveats to all of this.  Most of the evidence comes from maths, reading and science because there are the areas where data is readily available.  It’s also true that it can’t hurt to develop subject knowledge and teachers are often willing to spend their own time and resources on this; my aim isn’t to dampen their spirits as they do this.  But there are opportunity cost implications to choosing to devote time to content knowledge CPD whilst excluding pedagogy.

In subjects like Maths or Science, where content is integrative perhaps this feels like a non-problem.  Subject knowledge can be developed where it is weaker but more time can be spent on pedagogical subject knowledge (the subject of the next post).  But in accumulative subjects, like history, RE or Literature, you could spend a lifetime improving your just your subject knowledge and perhaps teachers feel the pressure to do that.  For more on the types of knowledge in the curriculum and these terms see this excellent blog by Rosalind Walker.

The biggest caveat is perhaps found in the question itself: teachers need to do more than know things.  Knowledge is only important in how it changes practice, which is why pedagogical content knowledge, the subject of the next post, is a better bet than content knowledge alone.

I’m conscious that one response to what I’ve said is that no one really thinks that they should just develop pure subject knowledge.  But as an idea becomes prominent, it morphs and mutates in ways we wouldn’t expect.  There will be schools where curriculum and subject knowledge development sit amongst excellent knowledge of students and evidence-informed practice and CPD.  Downstream from these schools the quality of these ideas is diluted into something more superficial.  Someone arguing that reading around your subject is the best CPD has an air of truth about it but it is not supported by the evidence.


Ball, D, Hoover Thames, M, and Phelps, G. (2008). Content Knowledge for Teaching: What Makes It Special?  Journal of Teacher Education. 59(5). pp 389-407.

Baumert, J and Kunter, M. (2006). The COACTIV Model of Teachers’ Professional Competence. In M, Kunter (ed) Cognitive Activation in the Mathematics Classroom and Professional Competence of Teachers.  New York: Springer Science and Business Media.

Baumert, J, Kunter, M, Blum, W, Brunner, M, Voss, T, Jordan, A, Klusmann, U, Krauss, S, Neubrand, M, and Tsai, Y. (2010). Teachers’ Mathematical Knowledge, Cognitive Activation in the Classroom and Student Progress. American Educational Research Journal. 47(1). pp 133-180.

Coe, R, Rauch, CJ, Kime, S and Singleton, D.  (2020). Great Teaching Toolkit Evidence Review.  Cambridge Assessment International Education.

Harris, D and Sass, T. (2007).  Teacher Training, Teacher Quality and Student Achievement.  National Center for Analysis of Longitudinal Data in Education Research. 

Hill, H, Rowan, B, and Ball, D.  (2005). Effects of Teachers’ Mathematical Knowledge for Teaching on Student Achievement.  American Educational Research Journal.  42(2). pp 371-406.

Hill, H and Chin, M.  (2018).  Connections Between Teachers’ Knowledge of Students, Instruction and Achievement Outcomes. American Educational Research Journal.  55(5). Pp.1076-1112.

Shulman, L. (1986). Those Who Understand: Knowledge Growth in Teaching.  Educational Research.  15(2). pp4-14.

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