Hi lilmisssunshine,
My dd was tested at 4 and 6, once with the SBV and once with the WISC. She scored slightly lower (5 points difference) on the SBV at 4 thn she did on the WISC at 6. Having tested at 4, personally I'd wait until your child was older if you can, for a couple of reasons. Firstly, dd got really tired at 4 and the tester struggled to get answer from her toward the end. She said this was not uncommon and can impact on the result. Secondly schools were reluctant to see the test as valid because of her age. On the otherhand now I have two tests verifying her scores so they're kind of hard to deny!