After years of progress, Newark Public Schools backtracked on a number of key performance measures last school year, including the district’s graduation rate, absenteeism rate, and college-readiness scores, according to state data released this month.

The city’s traditional schools did make modest gains on last year’s state tests, and former officials note that the district’s test scores and graduation rate had grown steadily for several years before last year’s dip. Experts also caution that one-year changes have little bearing on the district’s long-term trajectory, adding that the declines may not be statistically significant.

Still, the signs of stalled progress provide fodder for critics of the district’s previous aggressive changes, and complicate efforts by the architects of that overhaul to claim victory. The new data points could even become darts that U.S. Sen. Cory Booker, the former Newark mayor now running for president, will have to dodge as he highlights his education record on the campaign trail.

For now, the numbers give a boost to Roger León, who became superintendent in July. While León has mostly refrained from directly criticizing his predecessors, last year’s disappointing numbers bolster his argument that “dramatic changes” are needed, especially in student attendance and high school performance.

“All I have to do is look at our student attendance from last year — 86 percent — look at our student achievement data across our schools, to know that there’s a lot of work that needs to be done,” León said at a school board meeting Tuesday, where he vowed to eventually “redefine and redesign” the district. “We need to do a far better job at educating and preparing our students.”

The data, which the state published this month in its school performance reports, show that Newark’s traditional schools slipped from 2016-17 to 2017-18 on several benchmarks. The city’s charter schools, which educate about a third of students, saw their graduation rates and test scores rise last year.

Looking at district high schools, a slightly smaller share of students graduated, immediately enrolled in college, and passed Advanced Placement or ACT exams, which are used in college admissions. (SAT and PSAT scores also fell, but state officials said changes in how they were calculated could have affected last year’s rates.)

In the lower grades, the district’s scores declined in both English and math on a metric that compares student growth to that of peers across the state with similar past scores. But while their relative growth slowed, the share of Newark Public Schools students who met expectations on the state PARCC exams last year increased by about 3 percentage points in English and 1 point in math.

Across the district, a larger share of students also missed 10 percent or more of school days last year, qualifying them as “chronically absent.”

Mark Weber, a lecturer at Rutgers University and an education policy analyst, cautioned against reading too much into the district’s relatively slight backsliding last year.

“Small changes from one year to the next are almost always due to statistical noise,” he said in an email, “and not indicative of the success or failure of particular policies and programs.”

Former district officials, who declined to speak on the record, offered some context they said could help explain the declines. For example, they noted that far more students took the ACT last year, which tends to depress scores. They also said that as Newark students’ test scores rise, the state compares their annual growth to that of higher-performing — and often more affluent — peers across the state, effectively raising the bar each year. And they pointed out that more of the students who did enroll in college last fall chose four-year schools, which have higher completion rates than two-year colleges.

The former officials have also tried to shift the blame for last year’s graduation drop onto the new superintendent, by suggesting that his administration may have failed to remove former students from the rolls or help seniors make up missing credits over the summer — both of which could have dragged down the final graduation rate that was calculated last fall.

León, who could settle that debate, has declined to be interviewed; his spokeswoman did not respond to a request to comment for this story. But León referred obliquely to the former officials’ theory at Tuesday’s board meeting, saying last year’s graduation rate did not go down “because somebody in the new administration didn’t do what they were supposed to do.”

“In fact, my administration does know what it’s supposed to do,” he added, before suggesting that unspecified people under the previous administration were unqualified for their positions. “Ultimately, one of the issues we had is a serious problem in this school district where people were providing guidance without having the necessary certification to actually provide guidance.”

The question of who owns last year’s academic results — both the good and the bad — is complicated by a series of district leadership changes.

Newark’s state-appointed superintendent, Christopher Cerf, stepped down in February last year when the state ended its decades-long takeover of the district. An interim superintendent filled in for the remainder of the school year, after which León became the district’s first locally chosen superintendent in nearly 23 years.

Meanwhile, a yearslong debate has raged over the impact of the district overhaul led by Cerf and his state-selected predecessor, Cami Anderson, and promoted by former Mayor Booker and wealthy donors he enlisted. The overhaul, which began in 2010 and included school closures and new charter schools, outraged many educators and families and ushered in a temporary decline in test scores.

Scores eventually rebounded, largely driven by the expansion of the city’s high-performing charter school networks. But the city’s traditional schools have also made clear gains: scores have improved each year since the PARCC tests began in 2015, the graduation rate has increased by more than 14 percentage points since 2011, and students’ annual test-score growth remains well above 2012 levels even with last year’s decline.

Critics including Weber have questioned whether the recent improvements can be linked to the reforms, noting that similar districts saw test score and graduation rate gains during the same period. Whatever has driven Newark’s performance, its long-term trajectory has been “unquestionably upward,” said Jesse Margolis, an education analyst previously contracted by Cerf to study the overhaul.

“Despite modest declines on several measures last year, over the longer term, NPS has shown meaningful increases in test score performance, test score growth, and the graduation rate,” Margolis said in an email, adding that the city’s charter schools continued to show “substantial gains” last year.