In hindsight... and this is admittedly before my time... how much of that "progress" was just court-ordered suppression of racist policy?
15 years of judicial fascism from the Warren Court did more to crush racism in the South than even the Civil War... and with the schools reengineered and unions increasingly taking hold among the teachers, their children were implanted with the new, Correct Thought. The whole situation ought to send a chill down any freedom-loving person's spine because it established the model for justifiable fascism.
While some was court-ordered, like desegregation, it was mainly cultural, from my observations. What the cry was then, was "Equal Opportunity", not equal outcome. People wanted the chance to excel. Everyone wanted their kids to do well in school, the schools had Principals who were commanding presences (when the schools were integrated, my new principal was a huge black man, and he commanded respect--I liked him, too).
But the parents who could scratch the money together were pushing their kids to do well and get scholarships, academic or athletic, and get an education--become professionals.
Our school was about 25 miles from DC and outside agitators ginned up race riots and derailed all that. (One kid was busted by the FBI for running with H. Rap Brown and Eldridge Cleaver). While their parents (another 25 miles away) had basically thrown the troublemakers out of their community ("'Cause we ain't never had no problem with our white folks"), the infiltration of the schools, decrying the parents as Uncle Toms (and what may have inspired the Generation Gap for white kids as a tactic) was enough to subvert the parent's efforts. Soon, blacks were 'acting out', shortly after, the white kids decided they "have equal rights, too", and discipline was lost across the board. Education went out the window.
Things didn't calm down until pot became popular...and that wasn't a 'win' for anyone, either. Ignorant and stoned isn't any way to go through life.