Cynthia Stewart, 43, appeared before a federal magistrate Tuesday, the San Antonio Express-News reported. A bail and probable cause hearing was scheduled for Friday.
Federal investigators said in an affidavit that Stewart, who works at Olympia Elementary School in Universal City, Texas, originally became friends with the boy on Facebook. They eventually exchanged cellphone numbers and at some point the relationship became sexual in nature.
Investigators would not comment on whether Stewart and the teen ever met face to face or had sexual relations. His parents allegedly found 20 to 30 pictures of Stewart on his cellphone and called authorities.
Aubrey Chancellor, a spokesman for the Judson Independent School District, said the teen was not a student there.
Stewart's profile on the school site says she has been a counselor for 15 years after five as a teacher, that she is married and has a child.