Standardized test scores, which weigh heavily in the annual evaluations of some D.C. teachers, could diminish in importance under new guidelines issued by the District’s state education agency.

The potential change involves the D.C. public school system and 29 of 53 public charter schools in the District that are participants in the federal Race to the Top grant program. The District received a five-year, $75 million grant in 2010 to help lift the quality of teaching and learning in the city. Among the conditions is that 50 percent of evaluations for eligible reading and math teachers be linked to growth on the D.C. Comprehensive Assessment System, the citywide testing program known as DC-CAS.

But the Office of the State Superintendent of Education (OSSE) announced Wednesday that test score growth, also known as “value-added,” can count for as little as 30 percent of evaluations. Other performance yardsticks, such as SAT scores or quarterly “benchmark” tests administered by individual schools, can comprise the remaining 20 percent. The new flexibility was approved by the U.S. Department of Education at the District’s request.

“The time has arrived for a holistic measure of teacher evaluation,” State Superintendent Hosanna Mahaley said in a statement. “Flexible assessment options provide . . . a more comprehensive picture of both student progress and teacher performance.”

The proposed change in teacher evaluations was first reported Thursday by the Washington Examiner.

Sarah Wysocki, a young Fairfax County teacher at Hybla Valley Elementary, was previously fired by DCPS last year, despite good — even glowing — evaluations from the educators who did her five classroom observations. (Jahi Chikwendiu/WASHINGTON POST)

The current value-added proportion of 50 percent is a key element of the IMPACT evaluation system used by traditional D.C. public schools. A signature initiative of former chancellor Michelle A. Rhee, IMPACT triggers dismissal for teachers who receive a score in the “ineffective” range or two consecutive “minimally effective” ratings. Several hundred teachers, including more than 200 last year, have been let go for poor IMPACT scores.

At least 25 states have introduced or are developing value-added systems. The systems attempt to measure a teacher’s direct contribution to test score results, using a predictive model based on the previous year’s student scores. But some experts contend that the complex statistical tool should not weigh heavily in high-stakes personnel decisions. Test results can be skewed by too many external factors, they said, from poverty to illness to random events such as family emergencies.

There are also instances in which teachers can score well on the portion of the evaluation involving direct classroom observations of their pedagogical skills but have value-added scores that drag them into the “minimally effective” range.

D.C. school officials are working on changes to IMPACT that are expected to be announced this summer. There has been speculation that one of the modifications will be less emphasis on value-added. The school system would need Mahaley’s approval for the change.

Chancellor Kaya Henderson said revisions are under discussion but declined to be specific. “After we review the IMPACT data from this year (year 3), we’ll figure out what changes we want to make to ensure that IMPACT continues to be effective,” she said in an e-mail Thursday. “Additional flexibility — whether we use it or not — is always helpful, which is why we welcome the OSSE’s announcement.”

The state agency’s offer of flexibility is also a response to charter schools that have balked at creating IMPACT-style teacher assessments. Some charter educators have said they prefer to use tests other than the DC-CAS to measure teacher influence on student growth.

“Some of the schools have pushed back,” said Scott Pearson, executive director of the D.C. Public Charter School Board. “My interpretation of this is that it’s good. It’s giving schools more flexibility to use the assessments they want to use.”