But Duncan, who officially stepped down this week, leaves Washington as a deeply divisive figure. Over the last seven years, the Chicago native has aggressively implemented his vision for American education, in a more comprehensive way than perhaps any cabinet officer in the Obama administration has changed policy in his issue area. The rise of the Common Core education standards, a huge growth in the use of data in education and a strong push for accountability on colleges are among Duncan's signature projects.
Valerie Strauss, an education columnist at the Washington Post and strong critic of Duncan, recently called him "the most powerful federal education chief in the department's history."
"He definitely expanded the role of the Department of Education," said Tom Loveless, an education policy expert at the non-partisan Brookings Institution.
By wielding that power, Duncan has become the rare figure in an era of deep partisan polarization to be hated by many on the left and right simultaneously. The National Education Association, the nation's largest teachers union and a powerful force in Democratic politics, called for Duncan's resignation last year, arguing he was too supportive of standardized testing.
Earlier this month, Congress passed the "Every Student Succeeds Act," a replacement to the Bush-era "No Child Left Behind" law. Included in the ESSA, at the behest of congressional Republicans, are several provisions that explicitly bar the federal Department of Education from setting policy for all of America's schools. Republicans wanted to ensure there are no more Arne Duncans.
Mission accomplished?Duncan is one of only two members of Obama's cabinet (Agriculture Secretary Tom Vilsack is the other) to have served in his post since the start of the administration. And he will leave office having accomplished many of his goals.
Duncan helped convince 42 states to adopt education goals based on the Common Core, and 21 of them to use tests that directly align with those standards, which were created by a bi-partisan group and attempt to both make U.S. schools more challenging and the curriculum more similar from state-to-state.
While some liberals dislike charter schools, Duncan has been a strong supporter of them and presided over a huge growth in students attending charters in cities like Washington, D.C. and New Orleans.
He pushed through, over the objections of some university administrators, a comprehensive "College Scorecard" that creates a database that makes it much easier to figure out which schools don't do well in terms of making sure their students graduate and get jobs after college. Duncan quietly but dramatically changed America's college loan program, putting millions of students into a federally-funded program that caps loan payments at 10 percent of a person's income and forgives most loans after 20 years.
Duncan and his department have successfully urged school districts across the country to stop suspending students in kindergarten or elementary school, arguing such punishments are excessive and tend to disproportionately hit black and Hispanic students. He and his department also forced some colleges to overhaul their systems for preventing and investigating rapes on college campuses.
A move by both Duncan and Obama to highlight the importance of community colleges has created a growing movement, even in some Republican areas, to make tuition at those schools free. Amid the rise of for-profit colleges like the University of Phoenix, Duncan has been one of their strongest critics and used the power of his office to impose new restrictions on them.
"I came here very hopeful, also sometimes not sure what the federal government could do and be productive," Duncan told NBC News in an interview last month as he prepared to leave office. "It so exceeded my wildest hopes."
It's too soon to tell if these changes have made lasting impacts on improving college graduation rates, reducing the gap in performance between minority and white students, or getting test scores for the U.S. students closer to those of high-performing countries abroad, some of Duncan's primary goals
But national exams given recently to students in 4th and 8th grade across the country showed declines in student scores in math. And scores for black and Hispanic students remained much lower, compared to their white peers.
A fast startTaking over the Education Department in 2009, Duncan had unusually free rein to set policy. He had the strong backing of Obama, who had befriended Duncan when the two were leading figures in Chicago politics, and both the administration and Republicans in Congress were more focused on the economy and Obamacare than education.
And states had two problems that Duncan could help them fix. There was agreement on the left and right that No Child Left Behind was flawed. And in the midst of the recession, school districts were struggling to pay their bills.
Duncan offered states waivers to get out of the requirements of No Child Left Behind, as well as extra federal funding through a program called "Race to the Top" that was part of 2009 stimulus bill. But the conditions Duncan set for Race to the Top funding and an NCLB waiver were that states agreed to a group of reforms that the education secretary favored, such as creating Common Core-like standards and not limiting the expansion of charter schools.
By 2010, with little fanfare, Duncan had turned the Department of Education, traditionally a backwater cabinet post since the federal government provides only about 10 percent of the money for K-12 education (states and localities provide the bulk of the spending), into a powerful force helping set policy in nearly every state.
"The Obama administration has been very creative in their use of the bully pulpit to change education," said Anya Kamenetz, an education writer whose book "The Test" expresses skepticism about the growth of standardized testing under both the George W. Bush and Obama administrations.
"They had very little federal money. As much as he [Duncan] is criticized as a power-monger, he's been a very smart user of soft power."
But over the last two years, the opposition to Duncan's initiatives, particularly Common Core, turned into a movement.
On the left, many didn't like how the Common Core standards changed how math and English were taught. The standards put an emphasis on students reading non-fiction as well as fiction and learning broader math principles instead of shortcuts to answering addition or multiplication questions.
On the right, conservatives accurately cast Duncan as effectively federalizing education policy, dubbing his education policies as "Obamacore."
And the standards and tests were caught in a growing opposition from the left and right about standardized tests and using them to determine how schools, students and teachers are performing.
Amid the backlash, many states halted plans to use the Common Core tests, ending the administration's hopes of having students in nearly all states take the same examinations, which would have made it easier to compare schools and states to their counterparts across the country. Even in New York, a traditionally liberal state, about 20 percent of students opted out of taking the state's Common-Core aligned test earlier this year, another sign of the growing opposition.
"Politically, I think it was a mistake,"said Loveless, referring to Duncan's strong advocacy of the Common Core standards. "It then caused a reaction that caused a rollback. What the Congress did was they dialed back the powers of the secretary."
Duncan acknowledges this backlash but argues it is more about a failure to communicate his vision than his ideas themselves.
"How we talk about these things at the real level, to parents, to students themselves, I think has been mixed," he said in the interview. "We all need to continue to communicate clearly, to make mid-course corrections, to make adjustments."
Duncan is leaving office just as resistance to him has reached its highest point. But Duncan was not pushed out by Obama, who asked Duncan to stay through the end of 2016. Duncan says his family was ready to return to Chicago.
Duncan's replacement, former New York Education Commissioner John King, shares nearly all of Duncan's views, to the frustration of critics of both men.
'This stuff is sticking'The big unknown is whether Duncan's vision will outlive the Obama administration. Despite growing resistance to some of his ideas, the education secretary has set in motion a series of policies that will be complicated to unwind. Even amid the backlash over the Common Core, most states have kept the standards in place, in part because creating education goals and then training teachers in them is complicated and expensive.
Hillary Clinton has expressed skepticism about charter schools, but it will be difficult for her to stop their expansion in cities like New Orleans, where the majority of students now attend such schools. Clinton has embraced free community college and made it one of her signature campaign initiatives.
"The fact on the ground is that the overwhelming majority of states, be they left or right, blue or red or purple or whatever, they are moving forward with all of these things. This stuff is sticking," said Duncan.
He added, "Hopefully we have created a political climate, we've got to watch this, where when politicians start to want to reduce things going forward, hopefully there will be a public outcry against that."
Sarah Garland, executive editor of a non-partisan education news website called The Hechinger Report, said, "Politically, Common Core may be losing ground fast, but in terms of what happens in classrooms, this was a sea change for a lot of teachers."
"It changed how they do what they do. It will be hard to get them to go back," she added.
And Duncan, despite angering many on the left and right, will leave Washington with at least one friendship still intact.
"Arne has dedicated his life to the cause of education — and sometimes in the nicest possible way, he has gotten on people's nerves because he has pushed them and prodded them," Obama said at the signing of the Every Student Succeeds Act.
"Had he not been, I believe, as tenacious as he was, I think that we would not have as good of a product as we do here today. And so I could not be prouder of Arne Duncan," the president added.