Ability grouping in classrooms is back in fashion. Is this good for kids?

So, can high expectations coexist with differentiation in a diverse classroom, without grouping students by ability? Sure: when teachers provide intense extra help to move struggling students forward. But high-quality differentiation requires that teachers have enough time to provide students with one-on-one attention, which can be challenging in an age when so much emphasis is placed on test prep, and when class sizes are rising in many budget-strapped cities and states.

Source: Slate.