In terms of math and reading, American student scores of 17 year olds show little change in comparison 17 year olds of the early 1970s. Among minority students at various age levels, however, test scores have improved significantly.
The data is based off the scores of 26,000 students in public and private U.S. schools. The exam was the NAEP, the National Assessment of Educational Progress.
Miami Herald: The Nation's Educational Report Card
NationsReportCard.gov: 2012 Results