"In 2001, the National Center for Education Statistics found that 98 percent of public schools had drawn up acceptable use policies defining the ruls for Internet use on campuses. Of those schools, 74 percent were using some form of software to filter the Web's estimated 2.1 billion pages -- a number growing at a rate of 7 million a day."

Technology & Learning, January 2003
http://www.techlearning.com/db_area/archives/TL/2003/01/update.html