The lawsuit filed in Del Rio was first reported by the San Antonio Express-News.
It was filed Wednesday by one parent whose child was wounded in the shooting and two parents whose children were on campus at the time.
The lawsuit seeks unspecified monetary damages from the Uvalde school district, the city, law enforcement, a gun manufacturer, three individuals and others.
The defendants either declined comment or did not return messages. Attorneys for the parents say this is the first federal lawsuit related to the attack.