Studying the subject academically in any real capacity.
What do you mean by "in any real capacity"? I have read many books and academic papers about education. And I have experimented with some of the things I've learned. Does that count?
Among current K-12 teachers in the United States, what would you estimate is the median number of academic/research papers related to education or adjacent fields that they have read in the past 24 months?
in the US, every teaching degree requires
A teaching degree is neither necessary not sufficient for effective teaching. There are thousands of ineffective teachers with US teaching degrees. There are thousands of effective teachers without teaching degrees.