By Donna Lieberman

School should be a place where children are welcomed, encouraged and educated. Requiring over 90,000 students in New York City to pass through a metal detector, open their backpacks and sometimes submit to wanding and pat-downs in order to go to school everyday sends those students the wrong message.

These practices erect a barrier which makes students feel unwelcomed. They introduce a climate of suspicion and hostility where the students feel degraded and resentful of both police who administer the daily humiliation and of the educators who let it happen.

Administrators and students often complain about loss of class time and academic performance due to delays caused by lines at the metal detectors. And the vast majority of children subjected to these practices are black and Latino students, who are also disproportionately poor and vulnerable.

We all want schools to be safe. But research shows that metal detectors and street policing tactics that go with them do not improve school safety.

What's more, they are incompatible with the sort of nurturing and supportive environment that schools should work to cultivate.

A better way to promote safe schools is to focus on building trusting relationships between educators and students, so students feel comfortable seeking help when there's trouble .

Donna Lieberman is executive director of the New York Civil Liberties Union.