Matthew Effect: The rich get richer (faster) and the poor get poorer (faster).
It's an exponential virtuous or vicious cycle:
Good school attracts wealthier buyers, increase housing sale price, price-tied property taxes are higher, more money to fund ever better schools. Same wealthy buyers invest in the neighborhood and start/support businesses close to home, still more revenue for everybody. Revenue goes to more competitive teachers and more modern facilities, kids win awards and get into better colleges, publicity from "Winner High senior Edwin Smith gets perfect SAT score" generates even more attention both locally and across the ocean in emigrant communities. International buyers drive up home prices, transplant from other cities are told "just buy in Winner School District and you won't have to worry about Junior's education." Parents with disposable income donate it to the school district on top of their property taxes and still further improve the school relative to others by funding "extras" like TAs, music programs, etc.
MEANWHILE, every good thing that's happening in the prosperous school district is Oppositeland in the "bad school district." Bad publicity, less competitive teachers, fewer staff members and volunteers, more challenged students, more ELL students, dingier facilities. Up-and-coming young professionals with school-age children take off.
It's likely bad mojo for democracy but it does seem to be a real and pervasive situation.