Millions of students are finding major changes in the curriculum and battles over how teachers are evaluated, as the biggest revamps of U.S. public education in a decade work their way into classrooms

Updated August 26, 2013, 8:39 p.m. ET

Biggest Changes in a Decade Greet Students

Some Teachers, Parents Push Back on New Standards

STEPHANIE BANCHERO and ARIAN CAMPO-FLORES

Millions of students heading back to school are finding significant changes in the curriculum and battles over how teachers are evaluated, as the biggest revamps of U.S. public education in a decade work their way into classrooms. Most states are implementing tougher math and reading standards known as Common Core, while teacher evaluations increasingly are linked to student test scores or other measures of achievement. Meantime, traditional public schools face unprecedented competition from charter and private schools.Supporters say the overhauls will help make U.S. students more competitive with pupils abroad. But others worry that the sheer volume and far-reaching nature of the new policies is too much, too fast. Already, the changes have sparked pushback.

North Carolina teachers marched on the state capitol last month to protest lawmakers’ efforts to end automatic pay increases for teachers who obtain master’s degrees and plans to let children use tax dollars to attend private schools. In Texas, the birthplace of the student-testing movement, parents prodded legislators to scale back standardized testing of high schoolers. And some Indiana school boards passed resolutions opposing the state’s policy of giving schools letter grades from A to F after media reports showed officials tinkered with the formula in part to boost a charter school’s grade.

“This is the huge fulcrum moment for many of the reforms,” said Rick Hess, director of education policy studies at the American Enterprise Institute, a conservative Washington think tank. “It’s a lot messier than some might have thought.”

If a significant number of suburban, middle-class parents start pushing back, Mr. Hess said, “the whole reform agenda could blow a gasket.”

Randi Weingarten, head of the American Federation of Teachers, the nation’s second largest teachers union, predicted more turmoil as many states plan to roll out tougher standardized exams in 2015. Already, she said, the country has a “dispirited and demoralized teaching force at the very moment you need them to be at the top of their game.”

The last few years have seen dramatic changes in the U.S. education system, chiefly spurred by Republican governors and President Barack Obama. The president’s Race to the Top education initiative offered $4.35 billion to cash-starved states to adopt policies such as linking test scores to teacher evaluations and expanding charter schools, which are public schools run by outside groups.

Meantime, 45 states and the District of Columbia have adopted the Common Core math and language-arts standards, which lay out what students should know at each grade level.

More than 40 states have agreed to link teacher evaluations to test scores or other student-achievement measures, and four plan to rescind the licenses of some teachers who fail to make the grade.

Moreover, 14 states have passed laws allowing more charter schools and at least eight adopted or expanded voucher programs that let students use tax money for private schools. The number of charter schools grew to 5,997 last school year from 2,559 in the 2002-2003 year.

Now, many of these policies are taking root in the most striking remake of public education since President George W. Bush‘s No Child Left Behind, a bipartisan 2002 law that forces states to test students annually in math and reading and sanctions schools that fail to measure up.

Many of the current overhauls also shared rare bipartisan support and the blessing of some teacher unions when they were adopted. Ms. Weingarten, for example, has been one of the biggest champions of Common Core.

But similar to the history of No Child Left Behind, the cohesion is fraying as implementation kicks in. Common Core has come under attack from Tea Party activists who see it as an intrusion into states’ rights. They helped convince at least three states to back out of the common exams linked to standards. And Ms. Weingarten helped pressure Education Secretary Arne Duncan to offer states a one-year reprieve on linking test results to teacher personnel decisions.

Mr. Duncan in an interview said that implementing the new education policies can be “challenging, complex and messy” and that he expects to see “midcourse corrections” along the way. “People are struggling to do things that have never been done in the history of the country and that is hard work,” he said.

Chris Knez, a fifth-grade teacher in the Charlotte-Mecklenburg Schools in North Carolina, received specialized training in his previous school district in Common Core math concepts. That helped him teach his students higher-level skills, such as understanding the process of converting mixed numbers to fractions. Still, he worries the new Common Core exams won’t perfectly align with the standards, yet the results will be used against teachers. “You can’t pin so many consequences on something that seems to have such a shaky grounding in the first place,” he said.

In the Comsewogue School District on Long Island, N.Y., hundreds of parents, teachers and others rallied this month to criticize the state’s new and more rigorous exams. About 31% of New York state elementary students were deemed proficient in math and reading this year, down from 65% in math and 55% in English on the 2012 exams.

The blowback has been especially rancorous in Florida, a state long at the forefront of reshaping education. Parents opposed to some of the changes have formed organizations, testified at legislative hearings and mounted social-media campaigns, helping torpedo a “parent trigger” bill that would have allowed parents to demand changes at struggling schools. The parents groups saw the bill as paving the way for more charter schools.

In May 2012, the Florida Board of Education acquiesced to widespread outcry and lowered the passing score on the state’s standardized writing exam after a plunge in the number of students scoring at the proficient level. And last month, the state board voted to tinker with the A-to-F school-grading system to prevent schools from dropping by more than one letter grade.

Such modifications have “led to a lack of trust in this whole reform agenda,” said Kathleen Oropeza, who has two kids in public school in Orlando and co-founded a parents group called FundEducationNow.org.

But Patricia Levesque, chief executive of the Foundation for Excellence in Education—an organization created by former Florida Gov. Jeb Bush, who spearheaded many of the state’s education changes—, defends Florida’s standards. She said it is “really important for those of us who believe in high standards and accountability to do a better job of explaining what’s really occurring.”