But in the messy world, the best we can do is have a school system where we're reasonably satisfied that promising policies will be adopted and failed ones won't. It's no coincidence that school violence is mostly a problem of public schools. Public schools often have captive clienteles, especially in inner cities, and they know it. Just as important, private schools also have more freedom to experiment. In private schools, disciplinary policies aren't civil-liberties issues.
Private schools get to have private rules.
And freedom also means freedom to carry out grander experiments that would be unheard of in the public sector. Some think that all-girls' schools are safer for girls, chiefly because they have no boys. Catholic schools didn't achieve their remarkably violence-free record by only accepting rich white kids or by expelling troublemakers. In the inner city, Catholic and public schools are demographically similar, and Catholic-school expulsion rates are quite low. They rely on contact with parents, assertive discipline and strong moral values.