Fewer than six in 10 South Carolina students graduate in four years, according to a study released Wednesday.

The Palmetto State's ranking for its on-time graduation rate improved from the worst in the country to the fourth-lowest, according to Diplomas Count, an annual report published by the national publication Education Week.

Almost 56 percent of South Carolina students graduate in four years, which is far lower than the national average of nearly 71 percent but better than the state rate of almost 54 percent

the previous year, according to the 2004-05 data used by Editorial Projects in Education Research Center, which compiled the report.

The report estimates that 1.23 million students who were supposed to be in the graduating class of 2008 will fail to earn a diploma. Broken down, that amounts to roughly 6,829 students per day who leave U.S. schools.

"This is a crisis of really significant proportions," said Christopher Swanson, director of the center that conducted the study.

While the nation as a whole has improved its graduation rate in the past five years by 2.6 percent, "it's going to take a lot of time (to improve) if we continue to move at our current pace," he said. South Carolina ranks in the top 10 nationally for its improvement in its graduation rate for that same time period.

Researchers calculate graduation rates in different ways, which leads to varying results on South Carolina's actual graduation rate. This study calculated the rate by dividing the number of students in one grade into the number of students who were in the next grade the following year. It didn't count students who graduated in five years or decided to enter a GED program.

State officials hope to get a more accurate count of the state's graduates in the future. This is the second year that the state has assigned numbers to students to track them through high school.

All Lowcountry school districts, with the exception of Berkeley County, fell short of the state average, with graduation rates ranging from as low as 32.6 percent in rural Dorchester 4 to 53.4 percent in suburban Dorchester 2, according to the report. Charleston County schools' graduation rate was 46.7 while Berkeley County, which has maintained the best graduation rate locally for the past few years, was at 60.9 percent.

One strategy to help the state improve its rate could be setting annual graduation rate goals for every school and state, according to the Southern Regional Education Board, a nonprofit organization created by Southern elected officials to help improve the region's social and economic life. Few states have publicly set annual goals.

South Carolina's graduation rate goal under the federal No Child Left Behind law is 88.3 percent by 2013-2014. The state doesn't set annual goals, but the idea has considered by state education Superintendent Jim Rex.

State Education Department Spokesman Jim Foster said Rex wanted to wait to flesh out the idea further until the nation settled on a common graduation rate calculation method. Foster said Rex also would consider trying to include an annual graduation rate requirement in the state's accountability laws when they come up for review again.