Maryland students led the nation in growth in reading, science and math performance on a national test, according to a report released this week.

The analysis by a Stanford economist and Harvard education policy expert surveyed student performance on the National Assessment of Educational Progress between 1995 and 2009 to see whether reforms, such as the introduction of school accountability programs or increased spending on education, were making a difference in a yawning international achievement gap.

American students gained the equivalent of one additional year of learning over that time, they estimated. And in top-performing states, including Maryland, students acquired an additional two years of learning in the same period.

Florida and Delaware — where Maryland’s new Superintendent of Schools Lillian M. Lowery was recently education chief — came in second and third in growth. Virginia also landed in the top 10, along with Massachusetts, Louisiana, South Carolina, New Jersey, Kentucky and Arkansas.

Most of the states with the greatest growth are in the South, where the school accountability movement largely took root, the authors noted.

Meanwhile, students in Wisconsin, Michigan, Minnesota and Indiana were among those making the smallest average gains between 1992 and 2011.

Only 41 states were included in the analysis, based on available data.

Maryland’s education system has been recognized nationally before. Education Week magazine has named Maryland first in the nation for its education policies and student performance for four years running.

But while American students are improving overall, their growth is overshadowed by gains made in other countries, the report showed.

The analysis included progress on international tests over the same period and found that 24 countries appear to be improving at a faster rate, on average. Those countries include Latvia, Chile, Brazil, Portugal, Hong Kong, Germany, Poland, Liechtenstein, Slovenia, Colombia and Lithuania.