If you're wondering why homeschoolers have such a problem with testing, please read my FAQ about testing here: http://www.carolinah....com/afaq7.html.
Many families who refuse to test don't do it because they're scared their children won't do well. They refuse because it's not the best way to measure knowledge. It's the easiest one for the schools (and because they spend so much money on the tests, they don't have any left over to research better methods), but it has nothing to do with learning.
Other families refuse to test because their children have special needs or just don't test well. So test results are definitely not a valid indication of their knowledge.
I know where my children are academically because I'm here with them every day. They don't need to test every year just so they can learn how to take a standardized test. When my three oldest needed to take the SAT, they prepared for *that* specific test, and all three were given full-paid scholarships to college. (Speaking with over 20 years of homeschooling experience and as an ex-school psychologist, standardized testing should not be required - especially for those who don't want standardized children.)
I hope this helps if someone asks you about testing.