We present experimental evidence on a high-dosage tutoring (HDT) program implemented in three primary schools in a low-income neighborhood in the Netherlands. We document treatment effects of 0.28 national population standard deviations in math achievement scores (p<0.01) after one school year. These treatment effects are sizable and can account for roughly 40% of the math achievement gap between low-income and high-income students in the Netherlands. As most of the evidence on intensive tutoring programs draws on research from low-income settings in the US, our findings show that (i.) HDT programs can be successfully built from the ground up and exported to different institutional settings while maintaining meaningful effect sizes, and, (ii.) existing income-achievement gaps can be substantially reduced with practical and scalable interventions like HDT.