The Freedom from Religion Foundation asked a federal judge in Pittsburgh to declare as unconstitutional the display outside the front entrance of Valley High School in New Kensington.
The Madison, Wis.-based foundation said the marker serves to advance religion and the tenets of a particular faith. The lawsuit said a March letter to the school's superintendent did not generate an official response, and that local clergy held a rally during school hours to support retaining the monument.
Calls and email messages seeking comment from New Kensington-Arnold School District officials were not immediately returned.
The lawsuit requests an injunction ordering its removal, as well as the payment of damages and legal fees.