Experienced teachers and novices differ. That seems obvious. Experience must play a role. But how exactly do they differ?

A recent meta-analysis and review study by Xiao and colleagues tries to answer precisely that question by bringing together 45 studies comparing expert teachers with novices. Importantly, this is not based on opinions or self-reports, but on performance. And even more importantly, the study distinguishes between three components:

• knowledge,
• skills, and
• judgment.

Judgment can be understood as a teacher’s ability to interpret what is happening in a concrete, often complex classroom situation, determine what matters, and decide on an appropriate next step. The fact that this study looks at these three elements separately matters. In discussions about expertise, we often treat knowledge, skills, and judgment as one and the same, while they clearly are not.

The first result confirms what you would expect. On average, experienced teachers outperform novices, with a moderate effect size. This is not a trivial difference, but it is not a gap that explains everything either. The real added value of this study lies not in the overall difference, but in where it is located.

Differences in knowledge are relatively small and not statistically significant. This does not mean knowledge does not matter, but it suggests it is not a strong distinguishing factor between experts and novices. In other words, if you test teachers purely on knowledge, you will not necessarily be able to clearly identify who is an expert and who is not.

The differences are mainly found in skills and, even more so, in judgment. Skills refer to what teachers actually do in the classroom: classroom management, interaction, and the ability to follow what is happening in real time. Here, experienced teachers clearly outperform novices. But the largest difference lies in their ability to interpret situations and make appropriate decisions. This is where expertise becomes most visible.

This aligns well with what we know from broader research on expertise. Expertise is not simply an accumulation of knowledge and techniques, but the ability to use that knowledge functionally in context. Experienced teachers recognise patterns more quickly, see what is relevant, and act accordingly. Not necessarily because they know more, but because they see differently and decide differently. At the same time, other research shows that a lack of knowledge can still lead to problems, for instance, in classroom management. This is not an either-or story.

The study also shows that how you define and measure expertise matters. If expertise is reduced to years of experience, differences become less clear. When we use multiple criteria, or when measurements are closer to classroom practice, such as observations or video-based tasks, the differences become more pronounced. This suggests that part of the inconsistency in the literature may stem from how we attempt to capture expertise.

For practice, the implication is relatively straightforward, but not trivial. If expertise primarily manifests in action and judgment, then professional development cannot focus solely on knowledge. Knowledge remains a necessary foundation, but it is not where the difference is made. The core lies in learning how to interpret situations and make decisions in context.

That is also the part that is hardest to develop and to measure. Perhaps that is why it so often remains underemphasised.

Ultimately, this study makes explicit something many teachers likely already sense. Experienced teachers differ from novices, but not primarily because they know more. They differ mainly in how they look at what is happening in the classroom, and in what they do next.