What distinguishes someone who knows a subject from someone who knows how to teach it? The difference matters more than it seems. A mathematician may perfectly master a discipline and still fail to detect why a student has become lost in what appears to be a simple problem. An experienced teacher, by contrast, may modify an explanation halfway through a lesson, change the sequence of an activity, or reformulate a question because they perceive that part of the group has stopped understanding. This is not simply a matter of disciplinary knowledge. It involves interpretation, adaptation, and the constant making of pedagogical decisions.
That body of knowledge is what educational literature calls general pedagogical knowledge: the professional knowledge that makes it possible to organize learning, manage classroom dynamics, interpret difficulties, adapt teaching strategies, or assess understanding. For a long time, much of this work remained difficult to observe empirically. Systems could measure grades, attendance, investment, or school ratios. Much harder was measuring the specific knowledge teachers use when they teach.
That is precisely what the OECD is now attempting to do through the new Teacher Knowledge Survey (TKS), incorporated in 2024 into TALIS, its major international survey on teaching and learning. Conducted in eight countries, the study constitutes the first large-scale international assessment focused specifically on teachers’ pedagogical knowledge.
The report that attempts to measure how teachers teach
The Teacher Knowledge Survey does not assess whether one teacher knows more mathematics, history, or science than another. Nor does it measure charisma, creativity, or vocation. What it seeks to capture is something far more specific: the pedagogical knowledge teachers use when making decisions in the classroom.
To do so, the OECD incorporated into TALIS, its major international survey on teaching and learning, a specific assessment of general pedagogical knowledge (GPK), administered to around 20,000 secondary school teachers across eight countries: Chile, Croatia, Morocco, Poland, Portugal, Saudi Arabia, South Africa, and the United States. The central premise of the study rests on an important distinction: knowing a discipline is not the same as knowing how to teach it.
The report defines pedagogical knowledge as the set of specialized forms of knowledge that make it possible to create effective teaching and learning environments, regardless of the subject being taught. What does this mean in practice? It includes, for example, adapting explanations when a student does not understand, identifying misunderstandings, sequencing activities, maintaining the attention of a group, or interpreting assessment results in order to adjust instruction.
The assessment seeks to ground this knowledge in concrete classroom situations. Some questions, for example, present different ways of responding to disruptive behavior and ask participants to identify which approaches genuinely help sustain positive teacher-student relationships. Others present data from diagnostic tests before and after a pedagogical intervention and require teachers to correctly interpret the conclusions that can be drawn from them. There are also questions about motivation, metacognition, formative assessment, progressive management of difficulty, adaptation for students with dyslexia, and the differences between rote learning and deep understanding.
Rather than measuring adherence to a specific methodology, the test evaluates pedagogical judgment. Teachers are not scored for repeating a particular theory, but for recognizing which strategies are most appropriate in different learning contexts. In that sense, the report moves significantly away from the idea of teaching as the mechanical application of pedagogical recipes.
The design of the assessment also reflects an important shift in the way education systems are typically studied. Until now, much international information about teaching came from self-perception surveys: how strongly teachers believed they mastered a topic, how often they used certain practices, or how prepared they felt to teach. The Teacher Knowledge Survey introduces, for the first time, an objective measure of pedagogical knowledge — something long considered extremely difficult to construct in a way that would be comparable across countries.
The result is a much more precise picture of what happens in everyday teaching work. Because teaching, as portrayed in this report, looks less like transmitting information and more like interpreting complex situations in real time: detecting signs of understanding or disconnection, adjusting explanations, calibrating difficulty, sustaining the attention of diverse groups, and continuously deciding what to do next.
If pedagogical knowledge is associated with better learning outcomes, less time lost to discipline, and lower levels of teacher stress, then some education policies may have undervalued pedagogical training for years.
What happens in systems where teachers know more about pedagogy
The most interesting part of the report begins when the OECD stops asking how much pedagogical knowledge teachers have and starts analyzing what happens in systems where that knowledge is stronger. This is where some of the study’s most striking relationships emerge.
Better learning outcomes
Countries whose teachers achieve higher scores in pedagogical knowledge also tend to record stronger performances in PISA reading and mathematics. The OECD stresses that correlation does not imply causation and also notes that the analysis is based only on the seven countries that participated in both assessments. Even so, the pattern reinforces an important idea: pedagogy does not appear here as a secondary complement to disciplinary knowledge, but as one of the factors most closely associated with student performance.
Less time disciplining, more time teaching
Teachers with greater pedagogical knowledge spend less time maintaining order and more time on effective learning. In Morocco and Saudi Arabia, for example, an increase of one standard deviation in pedagogical knowledge is associated with increases of 16% and 22%, respectively, in time devoted to teaching and learning. The finding is especially relevant because effective instructional time has long appeared as one of the most important variables explaining differences in performance across education systems.
Adapting better does not mean producing more materials
The report also challenges some common simplifications surrounding personalization and active methodologies. Teachers with greater pedagogical knowledge are more likely to adapt explanations, take prior knowledge into account, and modify strategies when a student does not understand. However, they do not necessarily use more differentiated materials for each student.
This finding questions a widespread assumption within part of the contemporary EdTech discourse: that personalization means multiplying resources or building completely individualized pathways. What seems to make the difference here is not producing more content, but interpreting more effectively what each group needs at each moment.
Difficulty is also managed
Something similar occurs with more cognitively demanding tasks. Teachers with stronger pedagogical knowledge are not always those who rely most heavily on open-ended activities or problems without an obvious solution. In several countries, in fact, they show a greater tendency to progressively sequence task difficulty and better calibrate the level of challenge.
Teaching therefore appears less as the automatic application of innovative methodologies and more as the capacity to adjust pace, complexity, and support according to the specific context of the classroom.
Pedagogical knowledge also protects against burnout
Another of the report’s most significant findings concerns professional well-being. Teachers with higher levels of pedagogical knowledge report lower levels of stress related to student behavior, workload, diversity of needs, or administrative pressure.
This relationship does not mean that teaching ceases to be a demanding profession. But it does suggest that pedagogical knowledge also functions as a professional tool for managing the everyday complexity of the classroom. The finding also introduces an important dimension at a time marked by the crisis in teacher well-being and rising rates of professional attrition in many countries.
Differences within countries are enormous
The study also makes clear that pedagogical knowledge is not distributed evenly. In the United States, for example, there is a 175-point difference between the top 10% of teachers and the bottom 10% in pedagogical knowledge scores.
And although variation within schools tends to be greater than variation between schools, the report detects some concentration of the strongest teachers in certain schools, especially in South Africa. This matters because it suggests that part of educational inequality may also be linked to how pedagogical knowledge is distributed within school systems themselves.
What this report begins to change
If pedagogical knowledge is associated with better learning outcomes, less time lost to discipline, and lower levels of teacher stress, then some education policies may have undervalued pedagogical training for years. The Teacher Knowledge Survey places back on the table a fundamental question: how much specific knowledge does a person really need in order to teach well?
The issue becomes especially relevant in a context of global teacher shortages. Many countries are relaxing pathways into the profession and accelerating training programs in order to fill urgent vacancies. Part of these strategies rests on an implicit assumption: that pedagogy can be acquired quickly on the job. The OECD report does not completely invalidate those models, but it does suggest that pedagogical knowledge carries a far more structural weight than it was easy to demonstrate empirically for many years.
It also revives a deeper discussion: what kinds of expertise education systems actually recognize. Because much of what TALIS describes — diagnosis, adaptation, sequencing, or the continuous interpretation of learning signals — looks less like a secondary skill and much more like a complex form of professional knowledge.
And that may end up having important consequences for many current educational debates. Because if part of the differences between systems also depends on teachers’ pedagogical knowledge, then some questions begin to look different: how teachers are trained, how long it really takes to learn to teach, what kinds of professional development deserve priority, or what happens when pedagogy is reduced to a quick add-on within teacher preparation.
