I can't help you on the research, but you can point out that quite often twins are in the same grade as each other.

The IAS manual is a great tool, but this is where I think Belin-Blank went off course. You can be a perfect candidate for acceleration, but if you have a sibling the same age, or one year older - you are excluded.

--S.F.

For gifted children, doing nothing is the wrong choice.