Zero tolerance has been a common mantra in our nation's schools ever since the Columbine shooting nearly 15 years ago. School administrators adhere to this strict discipline approach to keep violence, and drugs, out of the classroom for the safety of students and faculty alike, and to ensure a positive, constructive learning environment.

We can all agree that the intention behind these strict policies is a good one. But as we've noted on this page before, sometimes school administrators go too far. The policies often spell out uniform and swift punishment for minor offenses such as truancy, smoking or carrying a toy weapon. Violators can lose classroom time or even end up with a criminal record.

Here are some of the examples we've cited in just the past year: A 6-year-old expelled for bringing a clear plastic toy gun to class; a second-grader expelled for tossing an imaginary grenade during recess; a kindergarten student expelled for saying she'll shoot a friend with a Hello Kitty "bubble gun"; a 5-year-old boy threatened with suspension from his school's after-care program after he crafted a gun out of Lego pieces and pointed it at other students; and a high school student expelled and arrested after her science experiment exploded. We should note that in this last example the incident happened before school hours when no other students were present, no one was injured and there were no damages.

The toll of tough discipline is clear: Secondary schools suspend or expel two million students each year, the Washington Post reports. Nationally, as many as 95 percent of suspensions are for nonviolent offense such as disruption, disrespect, tardiness and dress code violations.

"That's a staggering amount of lost learning time and lost opportunity to provide more meaningful support," Education Secretary Arne Duncan told the Post.

A landmark study in 2011 of nearly one million Texas students associated suspensions with academic failure, dropping out and involvement in the juvenile justice system. Consequences are important, Duncan said, but "I must ask: Is putting students out of school the best solution, the best remedy, for those problems?"

He said students should be removed from classrooms "only as a last resort," and only for serious infractions such as endangering the safety of other students or teachers.

On Wednesday, Duncan and Attorney General Eric Holder released what were described as the first national guidelines on school discipline, urging educators across the country to abandon overly zealous discipline policies that suspend students for minor infractions and send them to court instead of the principal's office.

The federal school discipline recommendations are nonbinding. They encourage schools to ensure that all school personnel are trained in classroom management, conflict resolution and approaches to de-escalate classroom disruptions -- and understand that they are responsible for administering routine student discipline instead of security or police officers.

The administration will propose a $50 million program to provide grants to more than 1,000 students to train teachers and staff in research-based strategies to improve approaches to student behavior and school climate.

These national guidelines are long overdue. There's a fine line between keeping students safe and ruining their academic careers (sometimes before they even begin). Hopefully these guidelines will provide schools with a blueprint to a balanced approached between keeping kids safe and letting them, well, be kids.