What can one say about Mayor Michael Bloomberg’s leadership of the New York City public schools that hasn’t been said before? After nearly a decade of mayoral control, the Bloomberg regime is the status quo.

Through most of that time, Bloomberg has justified mayoral control as a mechanism for focusing accountability for the achievement of New York’s 1.1 million students.  Mayoral control, he argued, placed him solely responsible for the system, and he should be judged by the results. If members of the voting public didn’t like what they were seeing, well, they could just vote him out of office at the end of his term.

The centralization of authority in a single individual paralleled a structure with which Bloomberg was highly familiar: CEO of a large, complex business. Bloomberg L.P., the company Mike Bloomberg founded, offers an array of financial and information services to hundreds of thousands of customers around the world. The company’s website describes its hallmark as “innovation and a passion for getting things right.”

That’s why it’s so disconcerting to hear the mayor hold forth on educational outcomes in New York City. Is he speaking as a CEO seeking to bolster his investors’ confidence in his products? Or do his public pronouncements reflect the assessments that he uses to guide the internal strategies of the organization? Does he respond to new information and incorporate it into his thinking? A certain amount of public optimism and embellishment would be tolerable if they were accompanied by a realistic appraisal of the successes and failures of his initiatives. Does the mayor truly understand the state of education in New York City?

Speaking at a panel on big-city school reform in Washington, D.C. on March 2nd, Mayor Bloomberg repeated a claim he’s made before: “We have closed the gap between black and Latino kids and white and Asian kids,” he said. “We have cut it in half.” It’s a claim that has never held up to serious scrutiny. Among the various scholars and journalists who have discredited this assertion are Nikhil Swaminathan, Sharon Otterman and Robert Gebeloff, Elizabeth Green, the Associated Press, theGotham Gazette, Jessica Shiller, Anna Phillips, and my colleague Jennifer Jennings and me (see here,here, here, and with Sherman Dorn, too), and me alone (here, here, and here).

Now, some of these analyses are a few years old, and the mayor was speaking just last week. It therefore seems like an opportune time to revisit the question using the most recent data available— the 2011 New York State test results, which report performance in English Language Arts and math for students in grades three through eight, and the 2011 National Assessment of Educational Progressdata for New York City, which report performance for fourth-grade and eighth-grade students in reading and mathematics.

I wanted to see if the magnitude of the average score difference between black and Latino students, on the one hand, and white and Asian students, on the other, had declined from 2003 to 2011. The year 2003 is an appropriate baseline for assessing what has happened under Mayor Bloomberg’s control of the New York City public schools because the law giving him control was passed in June of 2002, and the 2003 tests were administered relatively early in 2003, before any of Bloomberg’s signature reforms had been implemented.

Given the mayor’s penchant for reducing complex phenomena to a single number (Teacher Data Reports, anyone?), I have summarized the shrinkage in the achievement gap on the NAEP and New York State assessments as the percentage reduction in the gap. (For the technically-minded, this involved calculating group differences in citywide standard-deviation units, weighted by the size of the four racial/ethnic groups, for each grade and subject area, and then averaging those group differences, in both 2011 and 2003. The ratio of the 2011 group difference to the 2003 group difference indicates the extent of the change in the achievement gap over that eight-year period.)

So here it is: Looking across ELA and math scores on state exams for New York City students in grades three through eight in 2003, the achievement gap separating black and Latino students from white and Asian students was .74 of a standard deviation. In 2011, the achievement gap was .73 of a standard deviation. This represents a 1 percent reduction in the magnitude of the achievement gap. The careful reader will note that the mayor has thus overstated the cut in the achievement gap by a factor of 50.

What about for NAEP? In 2003, the achievement gap, averaged across reading and math scores in the fourth and eighth grades, was .76 of a standard deviation. In 2011, the gap was .78 of a standard deviation. Far from being cut in half, the achievement gap on the NAEP assessment actuallyincreased by 3 percent between 2003 and 2011.

Mayor Bloomberg said, “We have closed the gap between black and Latino kids and white and Asian kids. We have cut it in half.” But the gap has scarcely budged; it’s shrunk by 1 percent on the New York State tests, and increased by 3 percent on NAEP.

It’s the emperor’s new close.