I don't know what country the above poster teaches in, but in the US, home schooled students tend to perform above average.

"Standardized test results for 16,000 home educated children, grades K-12, were analyzed in 1994 by researcher Dr. Brian Ray. He found the nationwide grand mean in reading for homeschoolers was at the 79th percentile; for language and math, the 73rd percentile. This ranking means home-educated students performed better than approximately 77% of the sample population on whom the test was normed. Nearly 80% of homeschooled children achieved individual scores above the national average and 54.7% of the 16,000 homeschoolers achieved individual scores in the top quarter of the population, more than double the number of conventional school students who score in the top quarter."

http://www.hslda.org/docs/nche/000000/00000017.asp