In 2023, the ESTAFETT research team set out to tackle a question that many teachers and school leaders often ask—and have asked me over and over again: Does team teaching actually help students learn better compared to traditional, individual teaching? Although team teaching is widely adopted in schools, both in Flanders, where the study was conducted, and worldwide, evidence of its impact on learning outcomes is still relatively scarce. So ESTAFETT launched a carefully designed experiment in primary schools to find out. You can check the results here in Dutch.

In the study, 267 students from 7th and 8th grades (fifth and sixth if you count in the way grades are counted in Flanders), and 16 experienced teachers, participated. The researchers compared two situations: lessons taught by a single teacher and lessons delivered by two teachers working together. Both scenarios were set up as fairly as possible: the duplicate lesson content, the same teaching quality, and even the same preparation. To make the comparison even clearer, they chose science topics (forces and DNA) where students had little prior knowledge, and all teachers received detailed lesson plans and participated in workshops beforehand.

Here’s what they found: students made good progress in both setups. Right after the lessons, there wasn’t much difference between team teaching and individual teaching. But one week later, when the researchers tested what the students still remembered, the team teaching group pulled slightly ahead. Students taught in pairs seemed to retain the material a little better over time. The effect was small, but consistent.

One key detail? The student-teacher ratio mattered. The positive impact of team teaching was most evident when two teachers worked with about 30–35 students — that’s roughly one teacher for every 15 to 18 students. When the group size increased to 40 students (one teacher for every 20 learners), the advantage of team teaching disappeared. So it’s not just about having two adults in the room; it’s about keeping the group sizes manageable so that every student benefits.

At the same time, there’s a story of costs versus benefits that can’t be ignored. Team teaching, especially in optimal group sizes, remains an expensive intervention. Simply merging two classes of 20 students and having two teachers teach them together doesn’t automatically lead to better learning outcomes, but it does double the staffing cost. It’s no coincidence that organisations like the EEF for their toolkit now systematically look not only at the strength of the evidence, but also at the cost-efficiency of educational strategies. Team teaching can work, but it needs to be worth the investment.

Of course, like any study, there are limits. These lessons were meticulously prepared, and teachers had time to plan together — a luxury not every team teach duo has in real life. So, we shouldn’t blindly copy and paste the results into every school situation. Still, these findings match what international research is starting to suggest team teaching can make a real difference, especially if it’s well-organized and if schools keep a close eye on how many students each teacher is responsible for.

There’s more to come from this project too. Other parts of the ESTAFETT research will delve into why team-teaching seems to work, examining factors such as student engagement and psychological needs during lessons. Those findings will soon be shared on the ESTAFETT knowledge platform. But for now, one thing’s clear: if you want team-teaching to boost learning, think beyond just pairing up teachers — and pay close attention to group size, preparation, and yes, the budget too.