Sometimes a study appears that you seemingly cannot do much with. No intervention. No step-by-step plan. And no clear recommendation for what to do in the classroom tomorrow. You read it, nod, and are left with the question: so what now? The topic of subject-specific language in the classroom is explored in the recent large-scale study on mathematical vocabulary in classrooms, which is one such piece of research.

At first glance, the findings seem straightforward and yet unsatisfying. Teachers who use more mathematical vocabulary tend to have students who score higher on standardised tests. That association even holds when the researchers assign students randomly to teachers. But the picture complicates quickly. The same study shows that this vocabulary barely carries over to students themselves. When teachers use more terms, students do not automatically start speaking more richly or more precisely about mathematics.

Anyone looking for a quick route from research to practice runs into a dead end here. More mathematical vocabulary seems to work. And at the same time, it does not. Or at least, not in the way one might expect.

I hesitated before writing about this study by Zachary Himmelsbach. Not because it lacks quality, quite the opposite, but because it resists the kind of clear-cut takeaway we often demand. I came across the study via The Hechinger Report. That only increased my hesitation, as news stories tend to push research towards a single message. Yet this is precisely the kind of study that should not be reduced to a headline. It forces us, briefly, to stop acting and start looking more carefully.

The temptation is obvious. Turn the findings into a simple prescription. Use more subject-specific language. Be more precise. Avoid everyday words. But the study itself does not support that move. It does not show that mathematical vocabulary, on its own, causes learning. What it does show is that teachers who consistently use more mathematical vocabulary are, on average, more effective. The distinction is subtle, but it matters.

The most plausible interpretation, then, points to an indirect effect rather than a direct one. Mathematical vocabulary does not operate as a switch you can flip. It appears as a trace of well-structured teaching. It shows up when concepts are clearly defined, when representations are explicitly linked, and when examples are not just demonstrated but also named. In those moments, words like factor, ratio, or parallel emerge naturally. Not because teachers decide to insert them, but because the thinking requires them.

That also explains the apparent paradox. Mathematical vocabulary correlates with learning, but does not directly cause it. It is part of a broader constellation of instructional features that are associated with quality. Anyone who tries to copy only the visible element misses what actually matters.

Once you see that, the practical value of this research becomes clearer. Not in the form of a tip, but as a lens. It helps us look at explanations differently. Not: Do I use enough technical terms? But: when do I need words to support thinking? Where does my explanation remain implicit? Where do I let students act without making the underlying concept explicit?

In that sense, this is a study you can seemingly do little with. You cannot extract a checklist from it. You cannot build a professional development programme around it. And no, you cannot turn it into a simple message for a training day. And yet it is valuable. Because it shows where quality reveals itself, without pretending that it is easy to isolate or replicate.

Research does not always have to tell us what to do. Sometimes it is enough that it sharpens what we see. And sometimes, that is precisely enough.