> How can nothing have changed about the school? Schools derive a great deal of their funding from property taxes. You just described a school district dramatically gentrifying and going from 80% low-income to less than 15% low-income. The school now has a dramatically larger budget.

This is incorrect. All of the public schools in DC are in one school district, so the changing demographics of neighborhoods don't affect how much money is available for any given school in that district. The property taxes are all going into one pot.