Panelists called to testify before a U.S. House Education Committee hearing on school safety Wednesday agreed that arming teachers, or anyone else besides trained law enforcement officers, is a "risky proposition."

In the wake of the Sandy Hook Elementary School shooting in Newtown, Conn., state lawmakers from California to Virginia have proposed arming teachers as a way to protect schools and students, but the witnesses testifying before Congress said the outcome could be "detrimental."

"It's a very dangerous, risky proposition," said David Osher, vice president of the Washington, D.C.-based American Institutes for Research.

The chairman of the House Education Committee, U.S. Rep. John Kline of Minnesota's Second District, led the hearing, which focused on ways school leaders can help keep students and schools safe.

Osher and four others school officials and safety experts testified before Congress that school resources officers can be helpful but may not deter students or intruders intent on causing harm. Mo Canady, executive director of the National Association of School Resource Officers, said that roughly 10 percent of the nation's schools have trained resource officers.

"Your best protection is a trusting relationship between adults and students that encourages kids to share responsibility for their safety and share information," said Bill Bond, a school safety specialist with the National Association of Secondary School Principals.

Bond served as principal at Heath High School in Paducah, Ky., in the late 1990s when a 14-year-old opened fire in the school, killing three students and injuring five more. Bond and Frederick Ellis, director of Fairfax County, Va., schools Office of Safety and Security, stressed the importance of relationships.

"Yes, a [school resource officer] is armed, but the benefit of the SRO has little to do with the gun on his hip," Bond said. "... the most important SRO function is to build trusting relationships with the students."

The House hearing came as the Democrat-led Senate is weighing a ban on certain types of high-powered weapons, including assault rifles such as the one using in the Sandy Hook shooting. On Wednesday, the members of Congress and witnesses spent more time discussing student-counselor ratios and emergency planning than weapons and metal detectors.

"This [hearing] is about ways we can work together to help students feel safe," said Kline, who spent several days meeting with school officials in Minnesota during last week's congressional recess.

"Today's hearing stems from a heartbreaking event. But in order to have a productive conversation, we must try to focus on matters under this committee's jurisdiction."

Kline is among the targets of an online ad campaign pressuring Republican lawmakers to support expanded background checks for all gun buyers. The ads focus on Republicans that Organizing for Action think can be convinced to support the proposal.