A stabbing spree at a high school near Pittsburgh is a tragedy and serves as a reminder that children and staff deserve to work and learn in a safe environment, said U.S. Education Secretary Arne Duncan.

In a statement, Duncan said he is saddened and his thoughts go out to the victims at Franklin Regional High School.

When families send their children to school each day, Duncan said they expect their children to return home safely.

Twenty people were injured after a 16-year-old with two knives went on a stabbing and slashing spree. Among those injured was a school police officer who helped subdue the boy.

Duncan said the government will seek to assist and support students, school staff and the local community.

Meanwhile, President Barack Obama and first lady Michelle Obama sent their thoughts and prayers to the victims.

The president was briefed by his staff about the school attack on his way to Texas for a memorial service for last week's shooting at Fort Hood, said White House spokesman Jay Carney.