Now that we've tested our son, we're debating whether we should test our two younger ones, too. Knowing his giftedness has helped us a great deal in understanding him better and advocating for him. We wish that we had known sooner, so that we could've helped him (and ourselves!) better.

I've heard about "testing one, testing all", and also about how siblings might have scores that are within certain points from each other. Now, we suspect our youngest one is probably gifted, too, but she's only 5.3. So we'll probably wait until she turns 6. We're not sure about the second one. She's a bright and very creative girl. But so far, her teacher seems to challenge her at appropriate level. She's a very happy first grader in K/1 combo class, and her teacher lets a group of 1st graders work on 2nd / 3rd grade math.

My questions are these:
1. Aside from curiosity (us, the parents being curious, that is), why else should we do "test one, test all?" At this point, we don't think we need further accommodation. Of course things might change next year when she moves up to 2/3 grade combo class.

2. Is there a better time to test with WISC-IV? Our daughter will turn 7 in May. Does it make any difference to have the test done when she's 6, 7 or 8?

Thanks in advance!