Graduation rates in D.C. Public Schools jumped by nearly 3 percent last year, but fewer than three of every four students earned a diploma.

The increase amounts to about 123 more students with a diploma than in 2008.

The 72 percent of students reported to have graduated likely is inflated, though, due to a measurement used in the District and many school systems around the country that fails to account for every dropout.

A June study by Education Week based on the class of 2006, using a different measure, showed D.C. graduation rates to be less than 50 percent, for example. Chancellor Michelle Rhee said a more rigorous measure of graduation rates will be in place for the class of 2011, based on a student tracking system instituted at the start of her tenure in 2007.

Mayor Adrian Fenty called the results "encouraging," but stressed the schools had a steep hill to climb. He joined Rhee in the library of Northwest's Cardozo Senior High School for the announcement.

"We are headed in the right direction, and we are headed there fast," Fenty said, commending Cardozo for increasing its rate by about 9 percent.

In the pale-blue library, about five long rows of bookshelves lined with out-of-date titles took up a quarter of the room, and 14 computers faced a far wall. A lone magazine rack held a U.S. News and World Report from 2007, and several copies of the Week dated from September.

Principal Gwendolyn Grant said that when she arrived in 2007, the school had no library at all.

"We've made great strides," Fenty said. "But we're not yet where we want to be."

In a slight jab at the City Council, Fenty and Rhee stressed the importance of summer school to help students recover lost credits and thereby increase the graduation numbers. Rhee's decision earlier last year to fund summer school, despite the council's directive otherwise, was at the heart of debate in the fall over the need to fire teachers.

The graduation rates "show that we are engaging more kids in the high-quality education that we try to give them each day," Rhee said.

She also attributed the success to improved tracking of transcripts so schools can ensure students have the classes they need to graduate, and to an expansion of options such as night school and specialized academies within high schools.