City schools ranged widely in how often their students took a controversial fast track to making up failed classes, according to new Department of Education data.

“Credit recovery” offers students the chance to make up failed classes without having to repeat the entire course, often through online assignments or packets of worksheets. The option was designed for rare occasions, but critics of the Bloomberg administration say pressure to boost graduation rates caused the practice to be abused.

Education officials countered allegations of abuse by citing the fact that credit recovery accounted for just 1.7 percent of all credits earned citywide in the 2010-2011 and 2011-2012 school years.

But that figure masked the fact that many schools did not have any students earn credits through credit recovery, while dozens relied heavily on the practice, according to the new data, made available for the first time in response to Freedom of Information Law requests.

A GothamSchools analysis of the data found that at schools that used credit recovery at all, one in every 40 credits earned, or about 2.6 percent, came through the practice.

About a quarter of city high schools — 129 — did not award any credits through credit recovery in 2012, officials said.

That same year, 39 schools awarded more than 5 percent of their credits through recovery. At nine schools — mostly transfer schools and schools that were closing — that figure was above 10 percent, according to the city data.

At Mott Hall V, a Bronx school that expanded to high school grades in 2010, nearly half of the credits earned by ninth-graders in the 2010-2011 school year came through credit recovery, a fact that its principal attributed to staffing issues and students who took advantage of the program.

“They had no problem failing courses when they should have been doing what they had to do,” Peter Oroszlany said of some students who enrolled in credit recovery.

Oroszlany, who founded Mott Hall V as a middle school in 2005, said his budget was stretched so thin when the school expanded that he couldn’t hire enough teachers to handle all the incoming freshmen. Some students, he said, earned credits through a credit recovery course before ever taking and failing a traditional class, in violation of longstanding regulations.

“I did not have enough funding,” added Oroszlany.

Oroszlany said he was able to add more teachers the following year, and the school’s credit recovery rate dropped to 26 percent — still the third highest in the city.

Though Mott Hall V was an outlier, dozens of high schools still had credit recovery rates above 5 percent, about triple the city’s average, the data show. Some of the schools are transfer schools, or schools the city was phasing out due to poor performance. Those schools, which tend to serve very high-need students, have less ability to require students to retake entire classes.

At Franklin K. Lane High School, for instance, which shuttered in 2012, more than one in four credits that year was earned through credit recovery. At Bronx Regional High School, a transfer school that serves overage students who have failed at other schools, 27 percent of credits in 2011 were awarded through the practice.

Some schools with high-need, low-performing students leaned much less heavily on credit recovery. At West Brooklyn Community High School, a transfer school, just 11 out of more than 2,000 credits awarded in 2011-2012 came through credit recovery.

Many of the schools that used credit recovery sparsely or not at all were selective schools, where students tend not to fall behind often. At Brooklyn Technical High School, the specialized school that by far awards the most credits each year of any city school, just 12 credits out of more than 70,000 were earned through credit recovery in the 2011-2012 school year.

Despite rebutting allegations that credit recovery had proliferated inappropriately in many city schools, Department of Education officials announced in February 2012 that they would crack down on the practice as part of a broad set of policy changes designed to guard against graduation rate inflation. The changes followed an audit of crediting and graduation data at 60 high schools.

Starting last year, students can’t make up more than three core academic courses through credit recovery. They also are required to attend 66 percent of the class they failed in order to be eligible to take a credit recovery class. And students can now take credit recovery classes only in the same year as they failed their course.

Although the new policies did not take effect until the 2012-2013 school year, many schools used credit recovery less often in 2012, according to the city data. Oroszlany said knowing that the restrictions were coming influenced his use of credit recovery at Mott Hall V.

Another person said that as a principal, he made changes to his credit recovery policies more to stay out of trouble and out of public scrutiny than in the best interest of his students.

“We felt that if we didn’t find ways to keep up we would get killed on the P.R.,” said the principal, who declined to give his name because he did not want to discuss department policy publicly. But he added that the new restrictions were important because the “rules were ambiguous and people created their own interpretation.”

Some schools saw their credit recovery rates rise in 2011-2012, lending credence to anecdotal reports that some schools were encouraging students to make up missed credits before the new restrictions took effect. The Preparatory Academy for Writers in Queens awarded less than 1 percent of credits through credit recovery in 2010-2011 but used the practice for more than 7 percent of credits the following year, for example.

Some educators have complained that principals used credit recovery to inflate their graduation rates. That’s what seems to have happened at A Philip Randolph High School, where graduation rates soared by 30 points in 2009. A guidance counselor at the school later told GothamSchools that she was instructed to enroll dozens of failing seniors into online credit recovery courses just weeks before the school’s graduation day so that they could earn their diploma on time. The principal at the school, Henry Rubio, resigned that year amid an investigation into the school’s credit recovery practices. In 2011 and 2012, the school’s credit recovery rates were well below the city average.

Critics of the Bloomberg administration say the school’s story has been all too common.

“In a good credit recovery program, students who need to catch up on material they haven’t mastered would work on solid research and writing assignments, or conduct experiments in a science lab,” said United Federation of Teachers President Michael Mulgrew. “But once the DOE decided to count credit accumulation as part of a high school’s grade and a principal’s rating, in too many schools the answer to this problem was to have the kids spend a few hours plugged into a computer.”

This story was originally published on Sept. 23 at 11:19 p.m.