It took more than a decade, but the pendulum is finally swinging back from the rigid “zero-tolerance” policies adopted by school districts nationwide following the 1999 Columbine school massacre. Last week’s unanimous ruling by Maryland’s State Board of Education banned “zero tolerance,” requiring the state’s 24 school districts to adopt a more rehabilitative approach to discipline on a case-by-case basis and to use suspensions and expulsions only as a last resort.

This should have been the policy all along. A 2008 study found little proof that zero-tolerance policies increased school safety. But there’s ample evidence that they’ve undermined educators’ authority and credibility — for example, by criminalizing minor infractions and redefining butter knives and spitballs as dangerous weapons. The Bethesda-based National Association of School Psychologists noted that such polices result in a higher rate of repeat suspensions, indicating they are “ineffective in changing behavior for challenging students.”