The Stanford Achievement Test includes the Thinking Skills, Science and Social Science tests for 3rd grade and above only.

PCS is part of a growing movement of classical, Christian schools throughout Virginia and the United States.

Why does this growing classical education method  allow us to excel to this degree?

Further reading:

The Well-Trained Mind: What is Classical Education?

Escondido Tutorial Service: Why Classical Education?

The Lost Tools of Learning, by Dorothy Sayers