Former U.S. Secretary of State Hillary Clinton—who is trying to fend off a strong challenge from Vermont Sen. Bernie Sanders for the Democratic presidential nomination in the Feb. 1 Iowa caucuses—has one of the longest education resumes in the presidential race.

Over more the past three decades, she’s worked to expand access to early-childhood education, boost academic standards, and improve child health—but her track record of success is mixed.

In this year’s presidential contest, Clinton has attracted serious criticism for her education ideas from progressives, who think she’s not going far enough, and from the education “reform” community, which worries that her relationship with teachers’ unions is way too cozy.

Here’s what you need to know:

1. Clinton was a big fan of early-childhood education before it became the “it” edu-policy.

Clinton’s been on this one for a while. When she was first lady of Arkansas, she spearheaded an effort to bring a program known as Home Instruction for Parents of Preschool Youth to the state. As the country’s first lady, she helped champion the creation of Early Head Start (for low-income kids, birth to age 3). And as a U.S. senator from New York in 2007, she introduced the “Ready to Learn Act,” which would have added a preschool program to what was then a pending reauthorization of the Elementary and Secondary Education Act. (Her program didn’t come to fruition, but there is an early-childhood component to the new Every Student Succeeds Act, the newly-minted ESEA reauthorization.)

She also pitched a universal prekindergarten program as a presidential candidate back in the 2008 campaign, and again in this presidential bid. Getting it over the finish line will be a long shot though, even if she wins the White House—Congress has rejected a similar proposal from President Barack Obama. More on her record here.

2. Some in the education “reform” camp are really bothered by her campaign rhetoric, especially when it comes to charter schools.

Clinton has long been a charter supporter; she even said so in 2007 in a speech to the United Federation of Teachers, to audible jeers. But she made waves earlier this year when she said charter schools don’t take the toughest kids (unlike public schools, which have to take everyone). Since then, Clinton seems to be trying to rebuild her relationship with charter champions, even going so far as to say she likes the charter-friendly provisions in the Every Student Succeeds Act.

That may not be enough. Billionaire Michael Bloomberg is thinking about jumping into the presidential race, in part because he doesn’t like what Clinton has been saying about education, the New York Times reports.

3. Clinton voted for the No Child Left Behind Act as a senator, and is now a big ESSA fan. But she’s long been skeptical of evaluating teachers based on test scores.

Clinton supported the NCLB law back in 2001, but called for changes to it as a candidate in 2008. She was one of the first presidential candidates to congratulate Congress on passing ESSA. (Former Florida Gov. Jeb Bush, a Republican presidential candidate, is also a fan of the new law.) Clinton may have caught a lucky political break with ESSA’s passage; now she won’t have to choose between unions and the “reform” wing of the Democratic party on sticky issues like standardized testing.

ESSA doesn’t require teacher evaluation through test scores, but that probably makes Clinton happy. She wasn’t in favor of tying individual teacher pay to student outcomes back in the 2008 race, a big edu-difference between her and Obama.

4. She’s been endorsed by the National Education Association and the American Federation of teachers, but not all their members are so thrilled about it.

Clinton got the backing of the AFT back in the 2008 election, but she still didn’t get the Democratic nomination. The NEA, with all of its political muscle and money, didn’t endorse in the primary. Democrats, of course, then picked Obama as their nominee. And he championed some policies the unions really did not like, including teacher evaluation through test scores.

This time, the unions went in for Clinton early on, and many of their members are none-too-happy about it. They would have rather seen a Sanders endorsement, or at least a longer process, to give the unions time to extract policy promises from Clinton.

5. She’s an unabashed supporter of the Common Core State Standards and was active in the standards movement as far back as the 1980s, when she served as first lady of Arkansas.

In one her earliest campaign appearances, Clinton hugged the common-core standards, which many Republican presidential contenders have been dissing. And she was a fan of high standards long before the common core. As first lady of Arkansas, she worked to expand access to challenging courses. And in the Senate, she introduced a bill to create voluntary math and science standards. (It didn’t make it over the finish line.)

BONUS: Want to know who could be working on education and domestic policy during a potential Clinton administration? Get to know the team at the Center for American Progress. Many of the folks there, including vice president of education policy Catherine Brown and CEO Neera Tanden, are former Clinton aides. The AFT may be another hub of would-be Clinton staffers.

Want more? Check out our profiles of other folks who have a shot of winning Iowa: GOP Sens. Marco Rubio of Florida and Ted Cruz of Texas, and Vermont Sen. Bernie Sanders, who is going after the Democratic nod. And look forward to Andrew’s takeout on mega-real-estate developer Donald Trump, who is seeking the GOP nomination.