In education, the null hypothesis is that nothing makes a long-term, scalable, replicable difference. That is:
1. Take any pedagogical innovation or educational intervention.
2. Subject it to a controlled experiment.
3. Evaluate the experiment’s outcome several years later.
4. If the experiment works, attempt to replicate the experiment in more situations.
By the time you reach step 4, if not sooner, you will be unable to show that the innovation makes any difference in outcomes. What this suggests to me is that in the long run it is the characteristics of the students that determine outcomes, at least on average. Think of an individual student as “predestined” to reach a certain outcome. An educational intervention can disturb their path to the predestined outcome but will not change the outcome. I do not literally believe this model, but it is a null hypothesis that is difficult to disprove.