Sociologically you are right on target. The movement from family
farm to city in the US saw that phenomenon as farm kids went directly into engineering. The hispanic/black thing is a puzzling issue.
Our son, Parker--who was just admitted into FSU's college of Engineering if you haven't heard--was in a Math/Science/Engineering magnet school
here in Palm Beach County. The class president last year was a latina, but she was an extreme exception. Educators generally maintain that the school districts serving these populations lack the teaching resources and physical plants (labs, for instance) needed to turn out kids with solid backgrounds in science. It's a complex issue.