On the tape, which lasted little more than a minute, one of the sixth-graders can be seen having sex with two companions, El Manana in Nuevo Laredo reported Wednesday.
The students distributed video, shot in April, on the Internet. The video then was seen by a parent who recognized her son in the video, the newspaper said.
After reporting the matter to the school, the child's mother also complained to Campeche Attorney General Renato Sales Heredia who said the office is investigating, El Manana said.
Francisco Ortiz Betancourt, Campeche education secretary, said his office was investigating as well.