In a , pupils watch the explanation at home and do the exercises in class.
The logic is that a explanation can be paused and repeated, while a teacher cannot.
Class time is then spent on the part where pupils get stuck.
Trials report gains that are real but smaller than the enthusiasm suggested.
The gains also vary by household, which is the uncomfortable finding.
A pupil with a quiet room and reliable internet arrives .
A pupil sharing a room with three does not, and now falls behind in class as well.
Schools that made the videos available at school before the bell removed most of that gap.
Teacher is the second obstacle.
Recording a good explanation takes several hours and is done once.
Sharing recordings across a department is therefore the difference between a and a practice.
Few schools organise that, and most flipped projects end when the enthusiastic teacher leaves.
The version is not a method but a library that a department maintains.