It may sound like the kind of question you ask at the coffee machine rather than in a scientific journal: Is school absence contagious? Missing a day of school, that is surely an individual matter? A child is ill. Or, more honestly, does not feel like going. Or there is a lot going on at home. All of that is true. And yet, it turns out to be incomplete.

A recent study by Jacob Kirksey and colleagues, published in the American Educational Research Journal, did not examine schools in general or family background, but rather something much smaller and often overlooked. What happens inside a classroom when students are absent? And, crucially, what does that do to the others? And we know this can have huge consequences.

The researchers analysed millions of attendance records of fourth- and fifth-grade pupils in Texas, day by day. At the level of individual classrooms. What they found is uncomfortably simple. When more classmates are absent on a given day, the likelihood that a student will be absent the next day increases. Not a marginal effect, but a clear and robust one. When roughly 10% of a class is absent, the chance that another student will also be absent the following day almost doubles.

And before you think this is just about illness spreading, the effect remains when sickness-related absences are filtered out. This is not simply the flu or a cold doing the rounds. It also does not matter whether the absent pupils are high or low performers. The idea that it is mainly the absence of so-called “difficult” or “weak” students that disrupts the class does not hold here. Absence itself matters.

The frustrating part is that the researchers cannot directly measure why this happens. They do, however, outline a plausible mechanism. A class with many absences is unstable. Lessons slow down because pupils need to be caught up. Routines are interrupted. The social dynamics shift. For some children, that means extra unrest or stress. For parents, it may feel like “not much is happening today anyway”. And for pupils themselves, the threshold to stay home may quietly drop. Not as a conscious decision, but gradually.

What also stands out is that the effect persists beyond a single day. The elevated risk of absence persists for 2 to 3 days. Absence is not only contagious but also slow. Not an acute shock, but a subtle shift in what starts to feel normal.

This study rubs against a persistent reflex in debates about school attendance. We tend to locate the cause almost exclusively in the individual or the family. That is understandable, but too narrow. Attendance is also a collective phenomenon. Classrooms have a fragile equilibrium. When it is disrupted, everyone feels it, including those who do turn up diligently every morning.

This does not mean the solution is straightforward. More monitoring or stricter sanctions will not fix this. If anything, the study points in a different direction. Stability matters. How do you support absent pupils without slowing the whole class down? How do you ensure that returning after an absence does not create additional chaos? And how do you support teachers so they don’t constantly switch between catching up and moving on?

Missing a day of school is not contagious in the way a virus is. But it does behave like a social phenomenon. And that makes it a shared responsibility. Not only of parents and pupils, but of classrooms, schools, and systems. Anyone who takes attendance seriously should also be willing to look closely at what happens when someone is not there.