Anyone with young children, or anyone teaching first grade, sees it happen every year: somewhere between the ages of five and seven, a child suddenly seems to switch on a turbo for reading and maths. In just a few months, some children go from barely recognising letters to reading simple words, and from counting on their fingers to doing actual operations. We know that school plays a role in this, but how large is that role, exactly? And is it mainly age, or is it really the impact of schooling and formal instruction? In other words, a debate between teaching and maturation.
A new study by three Leuven-based researchers, Floor Vandecruys, Maaike Vandermosten and Bert De Smedt, offers a clear and surprisingly robust answer. They used an elegant quasi-experimental setup: the school-cutoff design. It sounds technical, but the idea is simple. They take advantage of something we take for granted in education but rarely stop to consider. Because children may start Year 1 just before or just after a fixed birthdate, there are groups of five-year-olds who are almost the same age but have very different amounts of school experience. That makes it possible to separate the effects of “getting older” from the impact of “going to school”.
The researchers followed 144 Flemish children from the end of kindergarten to a year later. One half started Year 1, the other half remained in kindergarten. And the findings are striking. They report strong and consistent effects of formal schooling on reading: letter knowledge and phonological awareness. Word reading in particular accelerates sharply for children already in Year 1. This confirms what many suspected: learning to read is extremely sensitive to explicit, structured instruction. Age alone cannot explain these leaps.
For maths, the picture is more nuanced. Schooling clearly affects arithmetic, digit recognition and symbolic comparison tasks. But another foundational skill, numerical ordering, shows little improvement during the first year of primary school. This refers to knowing which numbers logically follow one another. And before you think this means they weren’t ready: the major progress already happened in kindergarten. That makes the conclusion even more interesting: some early maths skills depend heavily on the environment and interactions in early childhood education, while others only really flourish later through formal instruction.
This also creates an intriguing asymmetry across domains. Schooling effects are large to very large for reading, but small to moderate for maths. At school entry, reading appears to depend much more on classroom experiences. Maths is distributed across two contexts: first, a foundation built in kindergarten, then acceleration through explicit instruction later on.
The study also reminds us of something simple but crucial: age alone does not determine what children can do. Two five-year-olds can be the same age yet have had completely different learning experiences. That is exactly why a design that separates schooling from maturation is so valuable.
Because this research took place in Flanders, it has some extra benefits. In our kindergarten system, almost all children attend, yet formal instruction remains limited. That combination creates early differences in skills, and Year 1 then reshapes those differences again. The finding that children already develop some foundational skills strongly in kindergarten strengthens the case for high-quality, rich early childhood education. And the clear schooling effects on reading show how crucial systematic instruction remains in the first year of primary school.
The work of Vandecruys, Vandermosten and De Smedt is a good example of how careful design and contextual insight can produce new understanding. It shows that reading and maths each have their own sensitivities to age, experience and instruction. And it reminds us that schooling is not a neutral backdrop to development but a powerful engine—though one that does not operate in the same way everywhere.