New York City’s four-year graduation rate fell slightly last year, from 60.9 percent to 60.4 percent, State Education Commissioner John King announced this morning in Albany.

King’s announcement, to the Board of Regents during its monthly meeting, set the stage for a press conference that Mayor Bloomberg and Chancellor Dennis Walcott have called for this afternoon. The annual graduation rate announcement is typically a festive occasion for the mayor, who has staked his education legacy in large part on increased numbers of students finishing high school each year.

But last year, when the city’s graduation rate flattened (showing a 0.1 point decline) after several years of steady growth, Bloomberg acknowledged that tougher graduation requirements could put pressure on the city’s graduation rate.

Students who entered high school in 2008 were the first required to earn a Regents diploma by passing five Regents exams with a 65 or higher. The less rigorous local diploma option, which for years helped prop up the city’s overall graduation numbers, disappeared, a change that critics said would leave thousands of students at risk of dropping out.

Statewide, the dropout rate last year was 3.5 percent, up from 2.7 percent in the previous two years, according to a report issued by the State Education Department earlier this spring. The increase was highest among students with special needs, whose “safety net” graduation rate option also vanished last year.

The city also made it tougher for students to earn the course credits and test scores required to graduate. City principals were required to limit the controversial practice of credit recovery, which allows students to quickly earn class credit through online work.

The city also began prohibiting teachers from grading exams taken by students at their schools, a practice seen as conducive to inflated test scores. Amid a citywide decline in Regents exam scores last year, schools that participated in a pilot of “distributed scoring” last year saw scores fall more than schools that did not. Citywide, just-passing scores fell by half.

“If you raise standards, it is going to be tougher to get everybody up to the same level,” Bloomberg said last year. “But we’re in favor of raising standards.”

Bloomberg does have some opportunities for spin when he takes the podium at City Hall this afternoon. Despite the decline, the city’s graduation rate is still about 15 points higher than it was in 2005. And two other big cities’ graduation rates fell even more: Buffalo saw its four-year rate drop by 7 points, and Rochester dropped by 3.4 points.

But Syracuse and Yonkers, which round out the state’s “Big Five” districts, saw declines that were smaller than New York City’s, King said. And the state’s overall four-year graduation rate held steady at 74 percent, he said.