Miami-Dade students improved their scores on two of four national reading and math exams, even as scores dropped nationally.
The results are from the National Assessment of Educational Progress, or NAEP -- also known as the "nation's report card." The test is given every two years in math and reading to fourth and eighth grade students.
The U.S. average scores dropped on each of the four exams -- with the greatest declines in eighth grade reading and math.
Education leaders said the latest national scores were surprising and disappointing, but said that scores have improved over the long term.
"The news isn't great," U.S. Education Secretary Arne Duncan told reporters.
Duncan said the cause for the decline in national scores isn't clear, but said the switch to Common Core math and language arts standards in more than 40 states and other new educational policies probably caused a downward dip as schools adjusted.
"This is not an infrequent occurrence," Duncan said.
The question is whether the dip is temporary.
"It was an unexpected downturn," said Peggy Carr, acting commissioner of the National Center for Education Statistics. "We need to see if it's a trend that will continue."
Results in Florida were mixed.
Fourth grade reading and math scores were flat, while statewide scores dropped on the eighth grade reading and math exams. Florida fourth graders scored higher than the national average on math and reading, but eighth graders scored at or below national averages in reading and math.
Among the nation's largest districts, Miami-Dade was singled out for posting higher scores on fourth grade math and eighth grade reading exams. But while scores in Miami-Dade are improving, the district was near or below statewide average scores on the four exams.
“The Miami-Dade County Public Schools simply hit the new NAEP test results out of the park,” said Michael Casserly, executive director, Council of the Great City Schools. “The school district’s gains were among the fastest in the country of any major city and were across the board, even as state and national numbers were trending downward.
The results weren't as positive in Hillsborough County schools, which include Tampa. Hillsborough's eighth graders scored lower on both the math and reading exams.