A US high school has been accused of spying on students at home through webcams in their laptops.

A lawsuit filed against the Lower Merion School District in Philadelphia claims laptop computers issued to students by the school came with remotely-activated webcams which it used to monitor their activities at home.

The suit also alleges the school kept its ability to activate the cameras secret from students and parents when the laptops were issued.

The surveillance allegedly came to light after Harrington High School assistant principal Lindy Matsko reprimanded a student for "improper behaviour in his home".

"Cited as evidence was a photograph from the webcam embedded in minor plaintiff's personal laptop issued by the school district," the suit says.

The boy's father then confronted Ms Matsko about the photograph and was told about the school's ability to turn the webcams on remotely, it claims.

The suit was filed on behalf of the student and his family as well as all other students and families who were affected. The Lower Merion district includes two schools with an estimated 1800 students.

It is alleged the school district, its board of directors and its superintendent violated several laws including the Computer Fraud and Abuse Act and the Civil Rights Act.