State and local school officials say California can take over a public school that habitually performs poorly, but it's never done so, leaving San Bernardino's low-performing schools faced with nothing but an empty threat.

While officials and experts disagree on the best way to judge schools' performance, they do seem to agree that federal and state education laws don't give schools much of a reason to improve.

The revelation points to a huge flaw in the nation's No Child Left Behind Act, which aimed to compel failing schools to get better.

"There has been no instance where either the federal or state government has stepped in and said, `This is unacceptable,"' said David Plank, an education professor at Stanford University. "It's not a genuine (threat). Districts don't take it seriously."

A day after saying the state could take over troubled schools, Fred Balcom, director of district and school improvement for the California Department of Education, said the state might not have that power after all.

"The California Constitution may prohibit us from doing that," he said.

Plank, executive director of Policy Analysis for California Education, a nonpartisan group run by Stanford University, UC Berkeley and the University of Southern California, said the emptiness of that threat illustrates a