I’m not sure that it’s accurate to say that the third study identified peer effects. Tracking does expose students to a different set of peers. It also exposes them to different class sizes, teachers, and instructional styles, as the authors note.
The study does show that this bundle of factors has positive effects on some outcomes, but it can’t be taken as evidence of the beneficial effects of any individual component of this bundle.
The authors even state in their section on mechanisms “it is unclear to what extent peer quality is driving our main effects”.
I’m not sure that it’s accurate to say that the third study identified peer effects. Tracking does expose students to a different set of peers. It also exposes them to different class sizes, teachers, and instructional styles, as the authors note.
The study does show that this bundle of factors has positive effects on some outcomes, but it can’t be taken as evidence of the beneficial effects of any individual component of this bundle.
The authors even state in their section on mechanisms “it is unclear to what extent peer quality is driving our main effects”.