In a dispute that touches the oldest tensions between institutional power and the free flow of information, New York City's largest charter school network has taken the state to federal court, alleging that a bureaucratic decision to withhold Advanced Placement exam data from a national ranking publication was not privacy protection but suppression. Success Academy, which serves tens of thousands of predominantly low-income students of color and claims extraordinary academic results, watched its statewide ranking fall from 11th to 196th when the missing data was replaced by metrics for program