We homeschool and choose to do standardized achievement tests (Iowa or Stanford) every year for two reasons: (a) to get the boys used to standardized testing (the lovely combination of boredom and pressure :-)) and (b) as a credential in case they want to drop into a school at some point and we need to document what they can do. HK has a good idea -- you can test at any grade level you choose.
There are a number of places (a Google search will reveal them) that permit homeschoolers (usually with a BA) to administer Iowa and Stanford. There are also
gifted tests and credentials you can pursue: we did Johns Hopkins CTY (a) to open up to us their courses and summer programs (very mixed) and (b) as a credential for schools (and, frankly, for hostile people who question whether homeschooled kids can possibly be keeping up with their schooled peers! :-)) You take the CTY tests at a testing center, but the tests aren't particularly long or hard (up through 6th grade; after that, they take the SAT or ACt).
