Four agencies have estimated progress in U. S. student achievement by administering waves of psychometrically linked tests in math and reading to nationally representative samples of students for selected periods over the past half century. Observed agency effects are attributed to differences in purpose, test design and sampling frame. Nonetheless, evidence across surveys from eleven million observations shows achievement gains consistent with the Flynn hypothesis that intelligence is rising. Gains are less steep in reading than math, though math increments may be diminishing. Greater progress is observed for students who are younger, non-white, and from low socio-economic backgrounds. Results are consistent with causal explanations that emphasize early-in-life improvements in nutrition, health care, and protection from contagious diseases and environmental risks.