D.C. Public Schools Chancellor Kaya Henderson announced Thursday that test scores will not play a part in teacher evaluations next year, a move meant to alleviate anxiety and account for unexpected complications as the city shifts to exams based on the Common Core State Standards.

Principals’ evaluations also will not include scores from the new exams next year.

“I want my teachers focused on teaching and not worried about whether or not the hiccups that come with implementing a new test are going to impact their livelihood,” said Henderson, who told teachers of the change in a letter Thursday.

Data from classroom observations will take the place of test scores in teacher evaluations next year, and the school system will continue to award bonuses of up to $20,000 to high-performing teachers at low-income schools. The school system will return to using test scores in the 2015-2016 school year.

The District was an early leader in using student test scores to evaluate educators, an approach that the Obama administration has pushed nationwide.

Henderson’s decision to pull back from that approach next year is a sign of the tension many states are confronting as they prepare to administer new and tougher Common Core exams while facing federal demands to hold teachers and principals accountable for student achievement.

Jason Kamras, the school system’s chief of human capital, said that no one should interpret the decision as a retreat from the school system’s commitment to the Common Core, the national education standards that have come under fire from both sides of the political spectrum. Nor is it a retreat from using value-added measures — a complex statistical tool that assesses a teacher’s direct contribution to student test scores — as key evaluation factors, he said.

“We continue to believe that student learning is a key indicator of teacher performance, and we believe that the fairest way to do that is value-added measurement,” Kamras said. “So we are 100 percent committed to returning to value-added” in the 2015-2016 school year, he added.

D.C. educators immediately praised the decision to delay using Common Core in teacher evaluations, calling it an important recognition of teachers’ concerns.

“It allows teachers the time to work with the standards and get comfortable with them,” said Wagma Mommandi, a science teacher at Cardozo Education Campus.

“It also gives the District the opportunity to provide quality professional development to support teachers in the transition and to work out any and all issues that will arise in this massive shift in assessment.”

Said Eugene Pinkard, principal of Marie Reed Elementary School: “It’s clearly the right thing to do.”

The U.S. Department of Education, which has often highlighted the District’s school system as a model for urban school reform, was lukewarm. “Although we applaud District of Columbia Public Schools (DCPS) for their continued commitment to rigorous evaluation and support for their teachers, we know there are many who looked to DCPS as a pacesetter who will be disappointed with their desire to slow down,” department spokeswoman Raymonde Charles said in an e-mail.

Under then-Chancellor Michelle A. Rhee in 2009, the District became one of the first jurisdictions in the country to link a teacher’s job security and compensation to student achievement on standardized tests. Since then, more than 400 city teachers have been fired for poor performance.

In 2010, the D.C. school system also became one of the first to implement the Common Core, which proponents say will better prepare students for life after high school by encouraging critical thinking and problem-solving instead of rote memorization.

States across the country have followed the District’s lead, many in pursuit of rewards — such as billions of dollars in federal Race to the Top funds and waivers from the most onerous provisions of the federal No Child Left Behind law — that the Obama administration granted to states that agreed to use student test scores in teacher evaluations. Most states also promised to adopt the new Common Core standards.

Those twin promises mean that the states are wrestling with how to fairly judge teachers according to their students’ scores on new exams. Some educators and officials who support the Common Core have called for accountability delays because they don’t want to see it derailed as the result of poor implementation.

The Bill and Melinda Gates Foundation, which has invested more than $200 million in developing and implementing the Common Core, last week urged states to hold off for two years before using the tests to evaluate teachers.

Previously, the leaders of the nation’s two largest teachers unions called for delaying test-based consequences for teachers as schools become used to the new exams.

Randi Weingarten, of the American Federation of Teachers, praised the District in a statement Thursday, saying she wished that the decision had been made sooner.

“If we are serious about making them work for every child, then we need to give teachers the time, support and flexibility to meet the individual needs of children — and that means focusing on learning first, not testing or rushing to impose high-stakes consequences,” Weingarten said.

Rhee called the one-year hiatus a “reasonable decision” and the “result of significant thought” that would still leave the District far ahead of the federal deadline for implementing test-based teacher evaluations.

Education Secretary Arne Duncan has resisted the call for a blanket moratorium on test-based accountability but has offered to consider individual states’ requests for one-year delays. At least five states have been granted a delay, according to Anne Hyslop, a policy analyst for the New America Foundation, a Washington think tank.

Even with a one-year hiatus, the District is “light-years” ahead of other states in using test-based accountability, Hyslop said. Many states are not slated to begin making personnel decisions based on test-based measures until 2017 or 2018, she said.

D.C. schools officials said they do not believe that they need permission for the one-year pause and did not formally seek a delay from the federal government, but they did notify the Education Department of their intent.

Officials with the Office of the State Superintendent, a citywide agency responsible for monitoring schools’ compliance with federal mandates, said they viewed the school system’s move as a proposal that OSSE can submit for federal approval only after soliciting feedback from the community.

The District’s move directly affects only teachers who have students in tested grades and subjects — about 15 percent of the city’s teaching corps. Value-added scores account for 35 percent of their overall score on the school system’s IMPACT evaluations; next year, that 35 percent will be replaced by data from classroom observations.

Test scores also play a large role in principals’ evaluations. Scores on next year’s Common Core exam will not affect principals’ evaluations.

Instead, Kamras said, the school system will use other measures of student achievement — such as scores on DIBELS literacy assessments for young children or on Advanced Placement exams for high school students — to judge principals’ performance.