This is an example from a tour several years ago, so may not be true anymore.
We toured both schools for lower school. Both schools told us about an optional, before school math club. At GDS, the kids in the math club played math related games. At Sidwell, the kids in the math club did worksheets, which were sent home with kids who were not in the math club (still optional).
We strongly preferred one of those approaches, but neither is objectively better than the other.