If you use other students for that problem instead of other teachers, you'd swap a budgetary problem for a bootstrap problem.

The upshot for this is that the benefit is as much for the student doing the teaching as the one doing the learning. Teaching has a much greater effect on _retention_ than listening reading or even doing, which is the majority determinant underlying the primary school curriculum.

There are a whole host of secondary benefits to this (as well as lots of logistical challenges): the students are doing something useful, teaching, and we pay teachers if you wanted to expend budget there I suspect it would have great effect, as would any other form of ~~bribery~~, I mean, incentivisation; socialising, especially if you have the teaching being done across different classes (which you would want to do because you want the teacher to know more than the student).