Quite right about learning in spite of the personality differences. Public schooling is best suited to the same personality group as that of the teachers, however, if there is discipline in the classrooms, the "other" types also learn. I can't answer your questions but I have some theories, amateur as they might be:
First, more is accomplished in a disciplined class so the other types can adapt and supplement with their own techniques. All students learn better in an atmosphere protected against distractions. For example, I learn best by writing things down and in classroom reading times, I could read quickly, outline the ideas and learn more that way than by discussing it with other kids as puzzled as I was. The method now seems to be having all the kids discuss it by getting in touch with their feelings.
Second, with the older system of classroom and education techniques, students had more flexibility to do class projects and homework that fitted their own personality types. I can remember a high school mythology project. Some students presented on ancient warfare. Some researched philosophy, or lifestyles. Some sculpted busts of Greek heroes. I wrote an "original" myth. And they were all individual efforts. No group projects, well, maybe one or two during my public school career but they were few and far between. My daughters had nothing but group projects where the most valuable thing they learned was not to trust their fellow group members to pull their own weight.
Third, formerly the personality types tended to self-segregate or be formally segregated into advanced, intermediate and slow classes or groups which reinforced each other while the teacher could challenge each student individually to live up to his or her potential. Now that type of academic segregation is considered politically incorrect. To the extent some of the brighter students are picked out, it is often to use them to teach the slower students, thereby slowing everyone up. Or worse, to hold the student up for praise in a classroom where students mock achievement.
Fourth, I think there was something to the idea that schools were not just an extension of personal lives. When we are at work we are all different personality types (although, as I mentioned, personality types gravitate towards certain careers and thereby continue grouping) but we also subordinate those parts of our personality that don't mesh with the work environment. The same thing happened, I think, to kids in school back in the dark ages. I never attended school in anything but a dress and I'm not that old (I hope, graduated high school 1970). It was just the dress code. One day a girl dared to wear a granny dress and she was sent home to change! (For those too young to remember, the granny dress was just what it sounds like: a dress granny might have worn. It had a high collar, long sleeves and a hem to the ground. The only radical thing about it was the psychedelic colors like pink and purple stripes mixed with pink and purple polka dots.) Today school kids dress like we used to when we washed the cars. And the teachers are, unfortunately, not much better. If you are in an environment where people look and act their best, their behavior is also better. Respect comes from appearances too. I know, I sound like an old fuddy-duddy but something important is lost when school isn't respected as a place to present your best face. Of course, nowadays, even work and church appearances are going downhill.
Fifth, education is not as valued today as it was back then. Back in the olden days, there were fewer safety nets for slugabouts. Parents continually stressed the importance of education as a way of getting ahead in life and gaining respectability. All personality types knew that education was a hoop to jump through, ill-fitting as it might be, to get to the real rewards in life. Today we have heroes and celebrities and millionaires who are rappers, cheating athletes, prostitutes and the like who made it without education. And, if by some unfair roll of the dice (to use Al Gore's analogy), the kids lose out on those avenues to wealth, what's the big deal? There's always welfare, scams, drug selling, identity theft, etc. Why bother to slog at work when there's no way to fail even if you won't work?
Today there is too much emphasis on entertainment and fluffy, politically-correct textbook and lessons. Computers often just become another source of distraction instead of instruction. The group is elevated above the individual with the plethora of group projects assigned. Teachers can barely move without risking lawsuits and poor evaluations by the administrators. Add to that the total disruption of the dress code, or lack thereof, for both students and faculty, and you have a very difficult learning environment. The noise level of our society is destroying the life of the mind. Computer buddies reinforce poor grammar, spelling, slang. Kids, and teachers and parents, are struggling against almost insurmountable odds to reclaim intellectual achievement as a worthwhile goal.
Just my humble opinion. What's yours?
Respect is a major problem. I hear the kids in the neighborhood arguing about "spect" all da time. Kids today are obsessed with gaining respect.
Of course the kids don't want to show any respect. They just want everyone to respect them without ever earning it.