You see, the students who failed at the interleaved problems initially, were rocking it when I had them work through like 3 of these 20-similar problems worksheets before moving on to the 'pedagogically designed' problems.

And epistemically I think it makes a lot of sense to train basics and build upon that.

I think Math education could benefit a lot if we split the subject in two courses, 3h per week on drill (Arithmetics), 2h per week on the beautiful math (can also expose the student to axioms there, functions, mappings, etc, more complex problems and solving that with math, potentially with CAS support). Best separated with different teachers.

Fact is, most high school graduates will find it challenging in their lives to apply the 'rule of three'. During the covid pandemic we have seen that members of the executive branch have no understanding of exponential growth (bad during the pandemic, but I wonder how the fiscal policy is affected by that??).

Maybe we need to rethink mathematical education once again.