Recent research suggests that using additional teachers to provide small-group instruction or tutoring substantially improves student learning. However, treatment effects on test scores can fade over time, and less is known about the lasting effects of such interventions. We leverage data from a Norwegian large-scale field experiment to examine the effects of small-group instruction in mathematics for students aged 7-9. This intervention shares many features with other high-impact tutoring programs, with some notable exceptions: instruction time was kept fixed, it had a lower dosage, and it targeted students of all ability levels. The latter allows us to assess fadeout across the ability distribution. Previous research on this intervention finds positive short-run effects. This paper shows that about 60% of the effect persists 3.5 years later. The effect size and degree of fadeout are surprisingly similar across the ability distribution. The study demonstrates that small-group instruction in mathematics successfully targets student performance and that effects can be sustained over time.
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