11 August 2009
"Drawing from 15 independent testing services, the Progress Report 2009: Homeschool Academic Achievement and Demographics included 11,739 homeschooled students from all 50 states who took three well-known tests—California Achievement Test, Iowa Tests of Basic Skills, and Stanford Achievement Test for the 2007–08 academic year. The Progress Report is the most comprehensive homeschool academic study ever completed."
This was such a comprehensive report, that I made a link to it from the right-hand sidebar. Check it out and refer your friends to it! What an up-to-date resource.