It almost sounds self-evident. Richer countries have better schools. So as countries become wealthier, student achievement should improve as well. A new study using more than twenty years of PISA data suggests the picture is rather more complicated. In this paper, Satoshi Araki makes a distinction that is surprisingly rare. Instead of simply comparing countries, he also tracks the same countries over time. And that is where things become interesting.

If you compare countries at a single point in time, you find exactly what we already know: wealthier countries tend to achieve higher PISA scores. The same applies, broadly speaking, to countries that spend more on education. But when you follow those same countries over two decades, a different pattern emerges. In many high-income countries, PISA scores declined while GDP per capita continued to grow. The study also confirms something researchers have known for quite some time: spending more on education does not automatically translate into better learning outcomes.

Araki therefore describes this as a paradox.

This does not mean that economic growth is bad for education. Nor does it show that better educational performance somehow slows economic growth. What it demonstrates is something much more methodological: relationships between countries are not necessarily the same as changes within countries. That lesson extends well beyond this particular study.

The paper discusses several possible explanations. Economic development may bring more distractions through digital technologies. Labour markets may increasingly value skills that PISA does not capture particularly well. Or perhaps achievement gaps become more visible simply because more young people remain in education for longer.

While reading the paper, however, I found myself thinking about another possibility that Araki does not mention. Many years ago, I had a conversation with Andreas Schleicher, the founder of PISA. During that discussion, we touched upon an idea that came back to me while reading this study. Perhaps good education simply becomes… normal?

When a country has had high-quality schools for decades, they gradually stop being something politicians or citizens consciously celebrate. Education becomes infrastructure, much like clean drinking water or a reliable electricity grid. People only notice it when it starts to fail. Paradoxically, the success of an education system may cause it to receive less attention. It becomes taken for granted.

That certainly does not mean teachers work any less hard or that schools suddenly become worse. But public and political attention can slowly shift towards other priorities, even though maintaining high-quality education requires continuous effort. The same applies to many educational goals, including basic skills. We tend to remember their value once children begin to lose them.

Anyone who has ever maintained a beautiful garden knows it does not stay beautiful simply because it looked good yesterday. I should admit that this particular analogy came from my wife as I genuinely know next to nothing about gardening.

I find this hypothesis at least as plausible as some of the explanations discussed in the paper. But at this point, it remains just that: a hypothesis. The study identifies an intriguing pattern; it does not yet explain it. That distinction matters.

Perhaps the greatest contribution of this study is not that it provides an answer, but that it asks a better question.

Not: Does economic growth improve education?

But rather: How can countries prevent high-quality education from becoming something they simply take for granted once they become prosperous?

That strikes me as a question educational research will be exploring for many years to come.