NEW YORK – New York City schools increased pay for school staff by nearly $159 million in the 2015-16 school year, bringing the city education department’s total payroll to an astounding $10.18 billion.

Much of the 1.57 percent spending increase over the previous school year is tied to a universal pre-K program pushed by Mayor Bill de Blasio. The program accounted for many of the 4,364 new school employees for the 2015-16 school year, though student enrollment remained steady at 1.1 million students, the New York Daily News reports.

MORE NEWS: From Classroom to Consulate Chef: Culinary Student Lands Dream Job at U.S. Embassy in Paris

“School workers also racked up nearly $22 million in overtime in 2015-16, up from just over $19 million the year before,” according to the news site. “Education Department spokesman Will Mantell said part of the increase in payroll spending was also due to raises paid to teachers under the 2014 teachers union contract.”

“Our investments in public schools are paying off, with pre-K for every four-year-old, record-high grad rates, and record-low dropout rates,” Mantell told the Daily News.

Brooklyn College and City University of New York education professor David Bloomfield contends that it’s nearly impossible to discern whether the significant spending increase is having a positive impact on students, or whether it’s a waste of money.

“The big numbers say little about quality or where efficiencies can be found,” he said. “Other independent analysis is needed to ferret out waste and abuse.”

Student proficiency data released by the school system finds in 2016, only 25% of 3rd through 8th grade students are proficient in math, while 40.5% were proficient in English.

Daily News analysis is based on city payroll data put together by the Empire Center, which runs the government transparency website SeeThroughNY.net.

MORE NEWS: Know These Before Moving From Cyprus To The UK

The Empire Center website shows the median teacher salary in NYC schools is between $71,000 and $81,000, while those in the 95th percentile rake in around $100,000.

But many educators in the city take home much more, including those with a history of failing or cheating students.

Former Brooklyn Boys and Girls High School principal Michael Wiltshire, for example, was the third highest paid school employee during the 2015-16 school year. That was the same year the school’s “quality snapshot” showed only a mere 58 percent of his students graduated on time, and only 56 percent graduated within six years.

Only 19 percent of students at the Brooklyn school successfully completed approved college or career preparatory courses, while only 7 percent graduated “college ready,” which means they did not need remedial classes, according to the snapshot.

The Daily News reports Wiltshire collected a bonus as part of his pay for school turnaround efforts before leaving his post in June to take over as principal of Medgar Evers College Preparatory School.

Also among the top-paid employees is former Bronx DeWitt Clinton High School principal Santiago Taveras, who took home a $198,149 salary in 2015-16.

“Taveras was removed from the Bronx school in November after an investigation found he fudged students’ grades,” the Daily News reports. “He remains on as an administrator in the Bronx.”

And the district’s top paid employee – City Schools Chancellor Carmen Farina – raked in $227,737, money collected on top of her state pension for working in city schools for five decades. That pension is worth $211,984 annually, according to the news site.