Metropolitan Nashville Public Schools officials say they're under financial siege from rapidly multiplying charter schools. And the state's three other large school districts -- including Hamilton County -- fear they're next.

So all four are clamoring for changes in the state's education funding formula, calling charters a "tipping point" for broader concerns about inequities toward large school systems.

School board members from the "Big Four" -- Hamilton, Knox and Shelby counties and Metro Nashville -- want Gov. Bill Haslam and state lawmakers to provide new funds to account for the growth in charter schools, which they say state policies are driving.

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