If asked to describe Mayor Bill de Blasio’s education agenda, most New Yorkers would likely give a two-syllable answer: pre-K.

As voters head to the polls Tuesday, when de Blasio is widely expected to sail into a second term, the mayor is surely pleased with that answer. His expansion of free pre-kindergarten to 50,000 additional four-year-olds has proven to be his clearest victory as mayor, earning praise from advocates, researchers, parents — even Hillary Clinton.

In fact, universal pre-K and its unexpectedly smooth rollout have proven so popular that de Blasio recently announced plans to launch a parallel program for three-year-olds.

“Our obligation is to come up with new solutions,” he said at a breakfast talk Monday with business and political leaders. “And so, we did that with pre-K and we look forward, with everyone’s help here, to doing that with 3-K.”

Pre-K hasn’t just provided de Blasio a happy talking point — it’s also helped him steer the discussion away from more controversial education issues, from charter schools to school segregation to his expensive support program from struggling schools, which has so far achieved mixed results.

“In many respects,” said Aaron Pallas, a professor at Teachers College, pre-K has “overshadowed virtually all other features of the education agenda.”

But another reason education has been a marginal issue in this year’s sleepy mayoral election — it didn’t come up at all during the first debate — is that, even apart from pre-K, de Blasio has overseen a period of relative stability and incremental process for the nation’s largest school system. Two of the most closely watched indicators of the system’s health — the high-school graduation rate and grade 3-8 test scores — have edged up.

The school system, Pallas added, “does seem to be generally moving in the right direction.”

Below, we recap de Blasio’s education record beyond pre-K and tell you what to watch for in his (expected) second term.

🔗A grab bag of initiatives meant to strengthen schools

Defining de Blasio’s vision for the city’s schools hasn’t always been easy.

Besides pre-K, much of his agenda has been a repudiation of the policies of his predecessor, former Mayor Michael Bloomberg, who closed dozens of low-performing schools, encouraged the growth of charter schools, and clashed constantly with the teachers union.

De Blasio has mostly halted school closures, instead flooding troubled schools with extra social services and academic supports. He’s been lukewarm about charters, drawing criticism that his administration has been slow to provide them space. And he revived City Hall’s relationship with the teachers union — which endorsed his reelection bid — agreeing to a significant pay bump in the new contract he negotiated.

In another union-backed effort, he’s funded over 215 “community schools,” which have embedded social-service providers, extended school days, and teams devoted to combating chronic absenteeism.

He’s also rolled out an assortment of initiatives called “Equity and Excellence for All” which, among other things, includes promises to make Advanced Placement classes available to all high-school students by 2021 and to provide computer-science courses to all students by 2025.

Besides some raised eyebrows about the long timeline, the plans mostly enjoyed a warm reception. They also fit within de Blasio’s education philosophy: If Bloomberg’s view was that the city school system was fundamentally broken and needed to be rebuilt from the ground up, de Blasio’s approach is to strengthen a system he says is in overall good shape.

The “Equity and Excellence” plans “were kind of presented as add-ons, instead of turning the whole system upside down,” said Clara Hemphill, director of education policy and Insideschools at the New School’s Center for New York City Affairs.

De Blasio said as much in his annual “State of the City” speech this February, when he touted the city’s record-high graduation rate, the new AP classes, and — of course — pre-K.

“The state of our schools,” he declared, “is stronger than many of us ever could have imagined.”

🔗Setbacks and crises force adjustments to the agenda

As much as de Blasio prefers basking in the strengths of the school system and his efforts to enhance them, some dark spots have proven inescapable.

Having vowed not to shutter troubled schools — but under state pressure to overhaul them — de Blasio was forced to come up with a turnaround program during his first year in office. He called the program “School Renewal,” and promised “fast and intense improvement” in the 94 bottom-ranked schools that would receive extra money and resources.

Three years later, the $582 million program has achieved mixed results — providing fodder for critics who say the effort is “mired in failure.”

Evan Stone, co-founder of Educators for Excellence, a teacher advocacy group, said he welcomed the investments de Blasio has made in Renewal schools but added: “The success has not been there.”

Some of the Renewal program’s critics — many of them charter-school backers who argue that charters are a better alternative to “failing” district schools — have also pounced on de Blasio’s school-discipline reforms.

De Blasio has made it harder for schools to suspend students, instead pushing schools to adopt  “restorative” practices where students reflect on their misdeeds and make amends. The new policies have continued to drive down the number of suspensions, but critics say they’ve made some schools less safe and orderly.

Those concerns flared up in September when a Bronx high-school student stabbed two other teenagers during class, according to police, leaving one dead.

City officials point to better attendance and academic performance at some schools in the Renewal program, and a record-low number of major crimes across the school system. And in the wake of the school stabbing, de Blasio’s schools chief, Carmen Fariña, unveiled a suite of new anti-bullying initiatives.

The stabbing wasn’t the only school crisis that forced de Blasio into action.

The number of homeless children has swelled during his tenure, with one in ten students residing in temporary housing at some point last school year — a grim new milestone that has left the de Blasio administration scrambling to help homeless students make it to school while trying to create more affordable housing for their families.

Meanwhile, since de Blasio rode into office in 2014 with promises to end the growing inequality that he called New York’s “tale of two cities,” advocates have pressed him to attack the city’s severe school segregation. After repeatedly insisting that the problem was a relic of historic housing policies largely beyond his control, he finally gave into the pressure and released a “school diversity” plan this June — which left many advocates underwhelmed.

“I hope that without the prospect of reelection,” Stone said, referring to de Blasio’s likely second term, “the mayor can be much more bold on desegregation.”

🔗What’s next?

If de Blasio’s first term has been about unveiling “transformative” education plans, his second term will hinge on executing and expanding those efforts.

That will include building out the new “3-K” preschool program, which the mayor has said will be even more challenging than the pre-K expansion.

He’ll continue to grapple with struggling schools in the Renewal program, which was billed as a three-year intervention and is now approaching its third birthday. De Blasio has said additional schools will close or be merged, while others might graduate out of the program, though the exit strategy for those schools isn’t yet clear.

And integration advocates are unlikely to let up. Even as they hold de Blasio to the goals laid out in his diversity plan, they also have signaled a desire to push him further — for instance, to revamp the high-school admissions process or invest in diversity-related teacher trainings and classroom materials.

It remains to be seen whether de Blasio will announce any major new education initiatives in the coming years — or a new chancellor to oversee them.

Among education insiders, there has long been speculation that Fariña — who was plucked out of retirement three years ago — will not stay on for a second term. If she does leave, her replacement could push the mayor in new directions, observers say.

“A new chancellor coming in could conceivably be more creative or bold,” said Pallas, the Teachers College professor, pitching ideas to the mayor “that are different from just, ‘Stay the course.’”

In a statement, a City Hall spokeswoman pointed to the higher graduation rate and test scores, lower dropout rate, and growth of free pre-K during de Blasio’s first term.

“The facts here are clear,” said spokeswoman Olivia Lapeyrolerie, “New York City public schools are the strongest they’ve ever been.”