Under the No Child Left Behind law, the definition varies from state to state. In Wisconsin, that means some troubled schools escape the law’s scrutiny.
Sarah Carr:

At Todd County High School in South Dakota last school year, 16 calls to police helped earn the school an unsavory distinction in the eyes of the state and federal government: The rural school was slapped with the label “persistently dangerous.”
Under the 6-year-old No Child Left Behind Act, each state must define a “persistently dangerous” school and allow parents to transfer their children out of them.
But at Milwaukee’s Fritsche Middle School, 187 calls to police over a recent six-month period did not make the school persistently dangerous under Wisconsin’s definition.
Neither did 263 calls at Bay View High School, or 299 at Custer.

Madison Schools’ police call data for Fall, 2006.