US school outcomes vary drastically. It really works out well in nice neighborhoods, and doesn't work out in some bad neighborhoods. Its down to cultural and familial expectations. Why does the same curriculum in say Scarsdale not have the same success in the Bronx? They are only like 15 miles apart in the same state.

The nice neighborhoods have parents that prioritize spending with their children, reading with them and helping them work through things they are struggling with and due to that they then score better on the standardized tests.

The curriculum is just a net zero, and could be argued that it's a net negative because it wastes the kids time with useless knowledge that they will never need or use.