Former Florida Gov. Jeb Bush listens before speaking at the National Summit on Education Reform in Washington. (AP Photo/Susan Walsh, File)

One of the big reasons that some Republicans suggest that former Florida governor Jeb Bush isn't conservative enough to be the party's presidential nominee is his longtime support for Common Core, a set of standards that lays out the skills students should have acquired by the end of each school year -- from kindergarten through high school. Many conservatives are strongly opposed to the standards, saying that they interfere with the right of local school districts to develop appropriate educational standards for their students.

Sen. Rand Paul (R-Ky.) has suggested that Bush's position on  Common Core will significantly detract from his appeal to voters in a Republican primary. "I think it will be a big problem," Paul said. Paul himself is a likely candidate for the GOP nomination.

The issue will almost certainly be a flashpoint in the 2016 Republican primary, perhaps the most divisive one. Here are seven key questions and answers to help you understand what Common Core fight is all about.

  1. What's Common Core, and where did it come from? 
  2. What do Common Core standards actually require of students and teachers?
  3. Which states are participating in the program -- and which states are resisting?
  4. What do states that are participating have to do?
  5. Why does Jeb Bush support Common Core?
  6. Why do other Republicans oppose Common Core?
  7. How do Democrats feel about the issue?

What is Common Core, and where did it come from?

Until recently, there were no national standards for what students in elementary and high schools should learn. A fifth-grade student in one state might be able to solve one kind of math problem, but wouldn't recognize the problems kids were solving in a fifth-grade classroom in another. Grade levels had little in common across the country. Since President Eisenhower first warned of this problem in 1959, repeated attempts to solve it have failed.

Several years ago, a group of politicians, experts and advocates were trying again to create a national system of standards. They persuaded Bill Gates to finance their project generously through his and his wife's foundation. Gates's staff then coordinated with the Obama administration, which encouraged states to adopt the standards.

That list of standards became Common Core. Most states have adopted it as a way of giving teachers and principals recommendations as to what kids should be learning.

The federal government is prohibited by law from interfering with certain decisions about how states and school districts teach kids. In order not to break this rule, the Obama administration simply said that schools that adopted standards of some kind would be more likely to receive federal grants. The administration didn't ask states to adopt Common Core specifically -- but since the standards were freely available already, many did anyway.

What do Common Core standards actually require of students and teachers?

A lot. In mathematics, the main idea is that students shouldn't just know how to solve a problem. They should know why that technique works, and they should be able to think about other techniques for getting the same answer. For example, it's not just enough just to remember mathematical shortcuts to answer questions. Rather, it's important to understand the concepts behind math. Here are two examples from Bush's pro-Common Core organization:

In reading, the idea is that teaching students how to read only gets them so far toward literacy. In order to be able not just to sound out words, but to understand what a writer is trying to convey, student need to be more familiar with the subject matter -- in other words, have more knowledge about the world around them -- or they'll be lost.

"This is one of the primary reasons middle-class and affluent children are primed for reading success relative to their disadvantaged peers," argues Robert Pondiscio. "Well-off kids are far more likely to bring to school the knowledge and verbal advantages that accrue from enrichment opportunities, educated parents, and a language-rich home environment—all of which pay big dividends in literacy."

That kind of thinking may seem sensible, but it has also created enormous controversy. The standards say that 70 percent of required reading for seniors in high school should be non-fiction. While that requirement supposedly applies to math, science and history as well, it's English teachers who are being asked to alter their syllabi most. They're frustrated at having to replace fiction, poetry and literary classics with Malcolm Gladwell essays, as The  Post's Lyndsey Layton has reported.

The National Review has assembled what it considers the most ridiculous Common Core questions.

Which states are participating in the program--and which states are resisting?

Most states have adopted Common Core, though many have done so with a curriculum that is named something else. Still, though, support is hardly universal--and in several key places, it is declining. Virginia, Nebraska and Texas have not joined, as the map below from U.S. News and World Report shows. Neither has Alaska, except for a few districts. Indiana, Oklahoma and South Carolina adopted the standards, but then repealed them. Minnesota adopted the standards for English and language arts, with modifications.

The standards are controversial just about everywhere. Missouri and North Carolina already have plans to get rid of the standards, and there are public disputes among state officials in Louisiana, Mississippi and Wisconsin about whether to continue using them.

What do states that are participating actually have to do?

Common Core does not specify exactly what teachers should teach, and it doesn't say that students must be tested, either. All the same, districts have redesigned their curricula around Common Core, and students in many states will be tested on the standards this spring.

New textbooks and assessments could cost between $100 and $400 or so per pupil, although estimates vary widely.

One of the more controversial questions about Common Core is whether teachers will be evaluated based on how their students do on the tests.

This summer, the Gates Foundation -- which helped developed the standards initially -- said that no test results should be used to evaluate teachers for at least two years. The foundation joined the two main teachers' unions in arguing that teachers need more time to become familiar with the tests in order to be judged fairly on their students' performance. Education Secretary Arne Duncan announced two months later that he would postpone a requirement that states use students' scores in evaluating their teachers.

The Associated Press has put together a useful summary of what Common Core means in all fifty states this school year.

Why does Jeb Bush support Common Core?

After leaving the governor's mansion in Tallahassee, Bush established a not-for-profit organization called the Foundation for Excellence in Education. He's been a forceful advocate of Common Core in his work at the foundation, which has received support from Gates.

In a speech last month, Bush laid out the reasons he supports Common Core. He argued that more rigorous academic standards in U.S. public schools will encourage students to try harder and learn more.

"This morning, over 213 million Chinese students went to school and nobody debated over whether academic standards should be lowered to protect their self-esteem," he said. His words recalled those of his brother, former President George W. Bush, about "the soft bigotry of low expectations."

Tom Loveless, a scholar at the Brookings Institution, rejects this argument. His research suggests that students don't do better just because they're expected to. Common Core was "built on a shaky theory," Loveless told The Post.

Another argument in favor of Common Core is that by setting common standards, the initiative will encourage educators and textbook companies to develop new approaches to teaching. This is a favorite argument of Gates's, who often uses the analogy of the electrical outlet:

“If you have 50 different plug types, appliances wouldn’t be available and would be very expensive,” he said. But once an electric outlet becomes standardized, many companies can design appliances and competition ensues, creating variety and better prices for consumers, he said.

If states use common academic standards, the quality of classroom materials and professional development will improve, Gates said. Much of that material will be digital tools that are personalized to the student, he said. “To get this innovation out, common standards will be helpful,” he said.

Why are so many Republicans opposed to Common Core?

The basic argument comes down to protecting educators' independence from federal intrusion. "I think most conservative Republicans think that education should be more at the state and local level," Paul said.

"We won't let the federal government take over Louisiana’s education standards," Louisiana Gov. Bobby Jindal, another Republican, has said. "We're very alarmed about choice and local control over curriculum being taken away from parents and educators."

While the federal government did encourage states to adopt Common Core, they didn't force the issue -- and education officials in dozens of Republican state administrations support the standards, including Louisiana. Superintendent John White, whom Jindal himself appointed, believes the state should stand by Common Core.

Polls on the question have produced wildly different results. Most Americans don't know much about the standards, and they don't have an opinion about them, so their answers will change depending on how Common Core is described in the question. That said, Gallup's research suggests that support among Republican parents is declining.

Anecdotally, the tea party movement are the Republicans who are most vocally opposed to Common Core, while the business lobby, including groups such as the U.S. Chamber of Commerce, is in favor.

How do Democrats feel about the issue?

It's hard to draw any firm conclusions from the data, but teachers are one important group of Democratic voters that are often opposed to the standards. Both major teachers' unions do support Common Core, but many members have become frustrated with the way the standards have been implemented. Polls conducted by Education Next found that 76 percent of teachers supported Common Core last year, but only 46 percent support the standards this year, with 40 percent opposed.

Educators who oppose the standards often feel that the lessons associated with Common Core are poorly designed, or say the tests are unfair. Supporters reply that if lessons or tests are badly written, then schools just need to find a better way of teaching students what they need to know to meet the standards. A phrase that you hear a lot is "Common Core is not a curriculum," which means that it is just a list of goals, not a complete set of instructional materials for teachers to use throughout the year.