Montgomery County Public Schools has the highest graduation rate of any of the 100 largest public school systems in the nation -- and the only rate above 90 percent -- according to a new study by a university professor.

The study compared the most recent graduation rates available for the nation's largest districts, using 1998 data compiled by the U.S. Department of Education. Since that time the county's graduation rate has continued to improve. Last year, the school system had the lowest dropout rate (1.71 percent) of any school system in Maryland.

The study found that the school system had a graduation rate of 90.75 percent, just ahead of Fairfax County with 89.52 percent.

Maryland also has been recognized as having the highest graduation rate of any state in the nation, based on the same 1998 data.

Overall, the range of graduation rates among the 100 largest districts includes the lowest at 26.26 percent for the Cincinnati City (Ohio) School District.

The study, entitled "Revisiting the Myth of the Texas Miracle in Education: Lessons about Dropout Research and Dropout Prevention," was authored by Walt Haney of Boston College. The study was presented at a Harvard University conference in January.