Different states have different testing requirements. In my state, I have only to choose a nationally-normed test, which allows me many options. For several years now, I've selected the CAT/5 Survey test. This is a short-form test, with six sections of 20 questions each, as opposed to the Full Battery.
Why the Survey test? Because it saves time and because it lessens the chances that the test will cover concepts we have yet to cover. I've found that the latter situation does nothing but ruffle my children's feathers and stress everyone out to a painful degree.
Why the CAT/5? Because homeschooling parents can administer the test at home. Another test option is the TerraNova, but I don't know anything about that one. I stick with what I know.
Then there's the ITBS and the Stanford Achievement Test. To administer the ITBS at home, a parent must hold a college degree and be accepted as a test administrator, which for me is one too many hoops to jump through. The Stanford also requires the degree as well as teacher certification and test-administration experience OR video training and pre-approval as a Stanford test administrator. Again, too many hoops.
Instead of giving the test at home, I could easily locate an ITBS testing center and drop off my daughters. For a few hours each day over three days. For a price, in terms of money, time, and stress. No, thank you.
There are several services that will mail you the testing materials and score the test for you. I've used both Family Learning Organization and Seton Testing Services with great satisfaction. Three others I've seen online are Thurber's Education Assessments, Crosspointe Educational Services, and Brewer Testing Services. But I don't have any experience with either of those.
As the girls move from middle grades to high school, I'll reassess my decisions on standardized testing depending on our needs. But right now, I'm happy with what we're doing.