One can easily look at the concept of a didactic lesson and tear it apart. All the pupils know and can do different things. They will all pick up new concepts at different speeds. They will all require different amounts of practice to master a new skill. Nuthall found that pupils already knew 50% of what was taught. The problem is, they all knew differing parts of the domain. It’s not like you can cull 50% of the curriculum, because different pupils didn’t know different thing.
Whenever the teacher is talking, what they’re saying will be unnecessary to a certain portion of the class. This sounds like a real problem, right? Little Jonny already understands how to add fractions. Why are we making him listen to it being explained again?
Prescription: individualised instruction and eradicating teacher talk. The drive for overwhelming differentiation and reduced explicit instruction does, in part, seem to have its roots in this noble aim not to waste pupils’ time listening to stuff that’s too hard or too easy*. All they want is for everyone to be in the goldilocks zone of optimal porridge temperature.