A Reading (RED'-ing) School District spokeswoman says Gerson Rivera resigned his post Friday. He had led the PTO at Tyson-Schoener Elementary School since the start of the academic year.
The online registry indicates Rivera was convicted in 2003 of possessing obscene materials in another state. He has been registered since 2004.
District spokeswoman Kristin Boyd says officials learned of Rivera's status last week.
Boyd also says Rivera has been asked to stay off school property while the district finds a way for him to be involved with his children's education.
Rivera could not be reached for comment.