When it comes to standardized tests, parents across the country are (a) concerned; (b) demanding change; (c) pulling tens of thousands of children out of the exams; or (d) making themselves heard at the top levels of government.

Answer: all of the above.

The backlash is kicking into high gear this spring as millions of students start taking new, more rigorous exams aligned with Common Core standards. Officials say the high-stakes assessments are crucial to evaluating student progress and competitiveness.

But a growing cohort of parents, students and teachers are rebelling against what they consider a toxic culture of testing. And officials, including U.S. Education Secretary Arne Duncan, have begun to listen as the grassroots movement engineers a series of high-profile rebuffs:

— Thousands of Colorado high school seniors walked out on new state-mandated science and social studies tests last fall.

— An Ohio middle school teacher published a letter calling state officials "bullies" for printing a pamphlet that warned of wide-ranging consequences if students sit out exams.

— At least 93 students at a single Philadelphia middle school are declining upcoming tests in a city that saw only 20 students districtwide sit out the exams last year.

The polite phrase for the burgeoning movement is "opt out." But testing opponent Morna McDermott, a Baltimore-area mother of two, puts it more plainly: It's a testing refusal movement — or a boycott.

"We're not doing this willy-nilly because we're a bunch of disgruntled soccer moms," said McDermott, who belongs to the national United Opt Out movement and refuses to let her children participate in Maryland's assessments. "This policy is harmful to our society, to our schools, to our teachers and to our children."

Federal law requires states to test students annually in grades three through eight and once in high school. But schools and districts have layered on their own assessments, leading students to take an average of 113 standardized tests over the course of their K-12 careers, according to preliminary research by the Council of the Great City Schools, a Washington-based organization representing large urban districts.

Test results measure student achievement but also can be used in teacher evaluations, overall school report cards and as high school graduation requirements. Opponents say the exams distract from real learning, put added stress on students and staff, waste resources and — especially in poor urban districts, like Philadelphia — contribute to the privatization of public education. Schools that score badly are sometimes turned over to management companies or become charter schools.

Some anti-testers would prefer an exam that samples random students to offer a snapshot without high stakes attached. Others support rating schools through an accreditation process like that used by colleges and universities. Accreditation includes site visits, in-depth analysis and a detailed action plan.

Pennsylvania saw 1,064 students statewide opt out of required math tests last year, a tiny percentage of the 803,000 exams given, but a nearly fivefold increase from 2011, according to the state Education Department.

In New York, about 67,000 students — almost 5 percent — sat out the statewide math test taken by 1.1 million of their peers last year.

Two teachers at Feltonville School of Arts and Sciences in Philadelphia have been holding informational meetings about opting out of the Pennsylvania System of School Assessment exams, which are given in April. The school serves mostly low-income students with many English-language learners and special education students — populations that traditionally test poorly.

Instructor Amy Roat said that it felt "unethical" not to publicize the little used opt-out option, and that she felt vindicated when the form letters they gave to students began coming back quickly.

"Very often you send papers home and they disappear into the abyss of someone's backpack, never to be seen again," Roat said.

District spokesman Fernando Gallard suggested parents are missing the bigger picture.

"We cannot live in a bubble," Gallard said. "We have to see how our kids are doing compared to the individuals they're going to be competing with."

Philadelphia has little recourse, since Pennsylvania law allows parents to refuse the test. But many states have no such policy, leaving individual schools to handle opt-outs on a case-by-case basis.

New Jersey lawmakers, responding to a growing clamor, have introduced legislation to allow parents to decline participation in the Partnership for Assessment of Readiness for College in Careers, or PARCC, exam.

The PARCC, which is debuting this year in New Jersey and 11 other states, is among the new generation of tests aligned to the Common Core — standards adopted by 43 states that outline the math and language skills students should master in each grade. Student achievement is expected to drop because of the new rigor.

The consequences of missing the exams are unclear and not uniform. In Illinois, the state board of education threatened to withhold funds from districts that don't administer the PARCC to all eligible students. Ohio officials warned that third-graders might not be promoted to fourth grade, and that some high schoolers won't get diplomas. In New Jersey, opting out could affect whether students qualify for gifted-and-talented programs.

Still, testing opponents can claim small victories. Pittsburgh cut out 33 hours of annual testing for some elementary students this year after re-evaluating its exam portfolio. Philadelphia's superintendent this week pledged to include opt-out information in districtwide handouts about the upcoming exams.

And Duncan, the education secretary, pledged last month to "urge Congress to have states set limits" on the amount of time spent on standardized tests.

"The call for thoughtful change from educators and families has been absolutely clear," Duncan said.

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Follow Kathy Matheson at www.twitter.com/kmatheson