New York City released good news on Wednesday: For the fifth year in a row, more students in the city are earning a high school diploma, reaching a record 74.3 percent.

“We see constant progress across the board,” said Mayor Bill de Blasio at a press conference celebrating the graduation rates. “Every borough, people of every background, the trend is so clear.”

But do increasing graduation rates reflect more students performing higher-level work? The question is complicated for several reasons. As graduation rates have climbed over the last few years, the state has simultaneously made it easier to earn a diploma. Additionally, earning a diploma does not mean students are ready for college. And the rates themselves may be deceptive; there are a variety of ways schools can artificially inflate them.

Amid a national conversation about whether graduation rates are a valid measure of student progress or whether they are inherently fungible, New York provides another example of how graduation rates can be a slippery tool for evaluating learning. Here’s our breakdown of the reasons to be skeptical of graduation rate data.

Reason 1: The state has eased graduation requirements.

New York has made it easier for students to earn diplomas in recent years though it is tricky to discern whether these changes are driving increases in graduation rates.

In the first — and likely most significant — change, students can opt out of a social studies exit exam and instead take a different test in subjects like science, math, arts or career and technical education. (Students are still required to take four other Regents exams in specific subjects.) The change was first implemented in 2014, but state officials have been adding alternative paths over the years, including allowing students to substitute a work-readiness credential for the final exam.

On Wednesday, state officials announced that 9,900 students took advantage of one of these testing or credential options in 2017. City officials said they estimate about 2,000 students used one of these options. (There are a little more than 200,000 students who began in this year’s graduation cohort statewide and about 73,000 of those students are from New York City.)

That is enough to account for a significant graduation rate boost, but State Commissioner MaryEllen Elia cautioned not to jump to that conclusion. Students who earned a diploma this way may have passed the social studies exam, in addition to completing a different path, but the school picked the second exam to record for official purposes. They also may have been able to pass the exam but chose another path instead, she said.

“We can’t draw any conclusions off of that by saying that one helped or didn’t help the other,” Elia said.

On top of that, more students can now appeal a failed exam. Previously, students had to score a 62 to appeal their score, but as of 2016, students can appeal a score of 60 or higher and they no longer have to adhere to an attendance requirement. Based on the city’s initial analysis, about 1,932 students took advantage of the appeals process, which is more than four times the number of students who graduated using this option before the state made this change in 2016.

Is there more? Yes. The state also eased graduation requirements for students with disabilities, who only had to pass two exit exams to graduate starting in 2016. This December, the state’s top policymakers eased the requirements further, allowing students with disabilities to graduate without passing any exit exams — a change that could affect future graduation rates. This year, the city estimates only about 230 students used this option.

Also important to note: These changes to graduation requirements were all made in the last several years. This year, graduation requirements were essentially the same and graduation rates still increased. However, teachers, students and schools had more time to prepare for and use the additional options.

Reason 2: Earning a high school diploma doesn’t mean you’re ready for college.

What does it mean to be a high school graduate in New York State?

Policymakers and advocates have long struggled to decide what a diploma should signify about a student’s accomplishments and knowledge. The lack of any formal definition is an important reason to be skeptical of using graduation rates as a marker of academic success.

Critics often point out that many graduates are not prepared for college-level work. Though 74 percent of students graduated in New York City last year, only about 64 percent of graduates earn high enough test scores to avoid remedial classes at CUNY colleges. (And that number is itself a moving target — it shot up this year in part because CUNY changed how it defines college-readiness.)

“Mayor de Blasio should hold the self-congratulation because the achievement gap remains too large, college readiness rates are too low, and watered-down criteria may explain gains,” said Jenny Sedlis, executive director of StudentsFirstNY.

Education department officials pointed out that the city’s college-readiness rate would have increased by 6 percentage points in 2017 even without CUNY’s changes — a sign that more students are leaving high school prepared for college, not just earning diplomas. In addition, more city students are enrolling in college after they graduate, the officials noted.

Reason 3: Schools can game their graduation rates.

A few years ago, New York City was rocked by a series of reports that schools were boosting graduation rates by changing grades or enrolling students in courses that fell far below the state’s standards. The practice, called “credit-recovery,” is meant to allow students flexibility if they fail a course, but was being misused in some cases to give students credit with limited instruction.

The problem of reporting faulty graduation rates is not confined to New York City. In Washington, D.C., it recently came to light that students received diplomas after missing too many classes. Chicago had to lower its graduation rate after inflating it for years. Tennessee couldn’t keep track of its own graduation rate last year.

There is no reason to suspect foul play this year, said Phil Weinberg, deputy chancellor, Division of Teaching and Learning.

“We feel very comfortable that we’re showing authentic gains here in the graduation statistic,” Weinberg said. “We have nothing that leads us to believe that anyone is trying to mess with stats.”

Christina Veiga contributed reporting.

Update: This story has been updated to note that city officials say the city’s college-readiness rate would have increased several percentage points last year even if CUNY had not eased its college-readiness requirements.