More than half of the New York City’s Hispanic students graduated from high school last year, the first time the city has reached that bar since it began tracking graduation rates in the 1980s.

That statistic stood out among several gains reported in graduation rate data trumpeted by Mayor Michael Bloomberg and Chancellor Joel Klein today. The city has nearly halved its drop-out rate over the past five years, and the number of students earning Regents and Advanced Regents diplomas rose, according to data released today by the city and state education departments.

“The results for New York City are historic,” said Bloomberg, speaking to reporters at the city Department of Education’s Tweed Courthouse headquarters this afternoon.

The city’s four-year graduation rates for students who entered high school in 2005 was 59 percent, up three percentage points from students the year before.

New York City’s gains compare favorably to those in the state’s other major urban districts. In 2005, the city reported roughly the same graduation rates as Buffalo, Syracuse, Rochester and Yonkers. But in the years since, New York City’s rates have risen more than 12 points, while the graduation rate for those four cities combined rose only 2.4 points.

Bloomberg used the data to promote the city’s conversion to mayoral control. He argued that even if state standards have become easier in recent years, as many critics have argued, the city’s growth compared to the rest of the state proves that the city’s gains are real.

Bloomberg and Klein also both argued the data released today demonstrated that the city was closing the achievement gap between white and Asian students and their black and Hispanic peers. But the head of the city’s principals union disputed that conclusion.

“We’re making some gains, but we’re not really closing the achievement gap,” said Ernie Logan, president of the Council of School Supervisors and Administrators.

The graduation rate for both black and Hispanic students rose by about 14 percentage points over the past four years, compared to approximately 10 point increases in the white and Asian graduation rates in the same period. Since last year, rates for all four demographic groups rose at about the same pace, with Hispanic students showing the highest jump of 3.1 points.

The number of students earning Regents or Advanced Regents diplomas also grew last year, while the number of students opting for the less-challenging local diploma shrunk. In 2009, 44 percent of students earned either a Regents or an Advanced Regents diploma, an increase of 3 points from the year before. By contrast, the number of students graduating with a local diploma ticked down a percentage point from last year.

Students earn a Regents diploma when they pass five Regents exams. The state is eliminating the local diploma option, which requires a student to pass only two exams or hit a lower bar on three exams, beginning with the graduating class of 2012.

Klein acknowledged that fewer students will likely graduate when all students are required to meet the more rigorous graduation requirements.

“But that’s exactly what we want to do,” Klein said. “We want to raise the standards and have our kids work up to those standards.”

Klein also admitted the city’s graduation rates for special education students and those learning English are lackluster, though the city did see gains for both of those demographics. The graduation rate for English learners increased nearly four points over the year before. That’s a much smaller gain than last year, when the city saw a 10-point boost in the graduation rates for English language learners.

Just under a quarter of special education students graduated last year, an upswing from 22.5 percent the year before.

Since 2005, the city has followed the state’s formula for graduation rates, which includes local and Regents diplomas and all disabled students, but does not count special education diplomas and GEDs.

One big question mark remaining in the city’s analysis is the degree to which schools’ credit recovery practices are driving increased graduation rates. At present, students recover credits from failed classes by completing extra schoolwork, but critics have charged that schools can easily abuse the practice to boost low-performing students toward their diplomas without mastering the material.

In January, city officials announced they would begin monitoring how schools grant credit recovery. But because new credit recovery standards and monitoring went into effect midway through this school year, data on the practice will not become available until the end of next school year, the city’s education data czar, Jennifer Bell-Ellwanger, said today.

Skeptics of the city’s data reporting have also questioned whether discharge rates for students have risen, distorting the graduation rate gains. (The city tracks the numbers of students who transfer to another school system, are expelled, graduate early or leave school after their 21st birthday separately from drop-out rates.) But according to discharge data the city released to reporters today, the number of students in the class of 2009 who left high school was the lowest since the class of 2005. The number of students who left the city’s high schools grew between 2002 and 2007, but then began falling, according to the data.

Here is the city’s complete presentation on graduation rates given to reporters today: