A massive experiment involving 17,000 students in four countries finds gains for inquiry-, or problem-based teaching over traditional approaches. Introducing math and science through inquiry and problem-based instruction can pay off throughout elementary school. However, while both boys and girls improved in inquiry-based classes, the researchers found that boys improved faster, widening the gender achievement gap.
Bando, R., Näslund-Hadley, E., & Gertler, P. (2019). Effect of Inquiry and Problem Based Pedagogy on Learning: Evidence from 10 Field Experiments in Four Countries (No. w26280). National Bureau of Economic Research.