I agree it starts in the classroom. Another thing that might be helpful is impose a year of mandatory service to the country after high school (not just military like South Korea and Israel), like Buttigieg and Sasse have talked about. You'd be forcing folks from all walks of life to work together for a common purpose that helps the country. I did a year of volunteer service between college and law school and found it enriching. I would think it would also produce a side benefit of giving kids from impoverished backgrounds job skills.