There are several out there I can't find the ones my wife and I looked at when we lived in a subpar school district. Below is a link and some excerpts from a CBS report.
http://findarticles.com/p/articles/mi_qa3955/is_200410/ai_n9443747/pg_4/?tag=content;col1
Many studies have been completed during the past 20 years that examine the academic achievement of the homeeducated (Ray, 2004b). Dozens of researchers have executed these studies. Examples of these studies ranged from a multiyear study in Washington state, three nationwide studies across the United States, and a nationwide study in Canada (Ray, 1994, 1997, 2001c; Rudner, 1999; Wartes, 1991). In study after study, the homeschooled scored, on average, at the 65th to 80th percentile on standardized academic achievement tests in the United States and Canada, compared to the public school average of the 50th percentile.
how home-schooled students at their institution compared to their general student population in terms of academic success. About nine percent said "far more academically successful," 22 percent reported "somewhat more academically successful," 38 percent said "academically about average," zero percent reported "somewhat less academically successful," zero percent said "far less academically successful," and 31 percent said "don't know."