Here's one thing I've heard about educational psychology
A study was conducted as follows - a sample of high-school pupils were given a test to assess the extent of their knowledge of the process of plant growth, which in fact takes place through photosynthesis as the growing plant constructs itself from CO2 in
the atmosphere, powered by the sun.
The children were then given a standard formal lesson on plant growth - an explanation, with diagrams, questions from the class and so on, designed for their age-group - and were again tested on their knowledge.
The surprising result was that, with statistically significant consistency, the scores were worse on the second test. The standard lesson had measurably decreased the childrens' understanding of the subject of the lesson - or so a straightforward reading of the results would suggest.
That's worth repeating. On average, they knew less after the lesson: the educational process had reduced, on average, their knowledge of the subject (as measured by standard evaluative techniques, using the normal rigours of experimental psychology.)
This astounding result turned out to be repeatable by other educational psychologists in other areas and countries.
I believe it was speculated by the researchers that the
decrease in the test scores was due to the excessive cognitive demands made by the format of the 'standard lesson': the demand to drop without question one's existing knowledge or thoughts on the topic, and accept (mostly) uncritically the unfamiliar explanatory concepts fired point blank, as it were, at the students. In effect, the demands of being a proverbial tabula rasa.
Interestingly, when teachers started their lessons by first questioning the pupils, in order to establish their existing understanding of plant growth, and constructing, in situ, a bridge from there to the target explanation, they were able to produce better results on the second test.
According to the summary I heard, these results were also repeatable.