Facebook, based in Palo Alto, accuses Teachbook of a slew of crimes including federal trademark dilution, trademark infringement and unfair competition.
"We think the complaint speaks for itself," said Michael Rhodes, an attorney representing Facebook. Teachbook did not respond to requests for comment.
Teachbook, based in Illinois, isn't launching until fall 2010 and many of the site's links are dead. Its homepage says it is a "teacher's community" where users can share lesson plans and seek advice from fellow educators.