It seems most everyone here is forgetting about one of the most visible causes of white flight during the mid to late 1960's, that being the infamous race riots that occurred in quite a number of cities from coast to coast. While it wasn't the underlying cause itself, per say, the riots were a direct result of the underlying causes (essentially direct as well as indirect racism), and they essentially brought everything to the forefront in a very visible, violent way.
Thankfully, at least for the most part (yes, I'm generalizing a bit here), that terrible era has been put behind us, finally. Now the biggest issue that remains seems to be the educational achievement levels in urban school districts, and resolving that seems to elude even the most well-intentioned reformers, unfortunately.
It's not just throwing money at the schools. Part of it is teacher, support staff and administrator training, part of it is definitely ensuring that urban schools have modern technology available just as suburban schools have, but a HUGE part of it boils down to ensuring students actually give a damn about learning, period. If students don't want to learn, if they don't want to put in the work, no matter how amazing the teachers are, it's simply not going to matter.
Frankly, the divides in our urban public schools are still the biggest problem getting families back into the core cities. Wealthier families pretty much always send their kids to private/parochial schools, while the working class/recent immigrants send their kids to the public schools, creating huge divides, both racially and economically. It's a huge issue, and one I'm not sure can ever truly be adequately resolved.
Aaron (Glowrock)