District education officials defended their decision to score the city’s 2013 standardized tests in a way that yielded gains in both math and reading, arguing Thursday at a D.C. Council hearing that it was the best way to demonstrate student progress as compared with prior years.

But facing aggressive questions and accusations of score manipulation from the chairman of the council’s Education Committee, officials acknowledged that they made a mistake when they failed to publicly explain their decision as they celebrated historic gains on the tests this summer.

Another grading scale, which educators developed to reflect proficiency on tests newly aligned to tougher Common Core academic standards, would have yielded a larger gain in reading but a decline in math. District officials decided not to use that scale after seeing how it would affect scores.

“We need to communicate much better to all stakeholders, and you can be assured that next year’s [test score announcement] will be a very different rollout with a great deal more outreach,” said Emily Durso, interim leader of the Office of the State Superintendent of Education, which administers citywide standardized tests for the District’s public schools.

Durso said that OSSE plans to publish the school-by-school proficiency rates that the alternative grading scale would have yielded. Officials plan to release those rates to the council Friday and publicly on the agency’s Web site Monday, she said.

That news did not mollify the Education Committee’s chairman, David A. Catania (I-At Large), who argued that the scoring decision was made “under the cover of darkness” to inflate student progress and stymie sweeping education legislation he has proposed.

“Honest government would have used the professionally developed cut scores to give children an honest assessment about where they stand,” Catania said, referring to the minimum scores students need to be deemed proficient in a subject.Based on the city’s decision, students who had fewer correct answers on this year’s more challenging math tests could have been shown as having improved over last year.

Catania argued that the content of the new tests was so different from previous tests that “proficiency” no longer means what it did before. The District’s test vendor is developing a definition of the skills needed for proficiency on the 2013 tests.

“The administration goes out and tells everyone that we’ve made dramatic improvements in proficiency, and we have no definition of proficiency,” Catania said.

He also questioned why OSSE rejected the new grading scale only after seeing the impact it would have on proficiency rates. According to public documents and city contracts, the agency had been planning to adopt the new scoring method for more than a year.

OSSE officials said that the agency’s leadership, which has undergone substantial turnover in the past year, did not know that the agency was planning to adopt new grading scales for the tests. Jeffrey Noel, OSSE’s director of data management, took responsibility for testing in June and chose not to adopt a new grading scale but to instead hold difficulty constant — a method that is generally accepted as reasonable and that allowed proficiency rates to be compared across years.

Catania, a lawyer, began the hearing by reading from an eight-page timeline of events, and he then peppered Durso and her colleagues with questions. The council chamber at times felt like a courtroom; Catania interrupted witnesses and accused them of “dancing” to avoid answering.

A spokesman for Mayor Vincent C. Gray (D), who has battled with Catania over education policy, compared the session to a McCarthy-era hunt for a conspiracy that doesn’t exist. “It’s chilling to see that,” Pedro Ribeiro said.

Catania adjourned the hearing to allow Abigail Smith, the deputy mayor for education — who had a family emergency — to testify at another time. His staff said the hearing is unlikely to resume if city officials publish the alternative test scores.

Results on the National Assessment of Educational Progress — a test given to students across the country every two years and considered “the nation’s report card” — are expected to be released soon. Those scores should provide an independent comparison of D.C. students’ academic progress to those in other states.

Meanwhile, there is a lingering legal question about whether OSSE has the authority to make final decisions about test-grading scales. While OSSE’s general counsel believes that the agency does have that power, council member Marion Barry (D-Ward 8) pointed out that city law gives the elected D.C. State Board of Education the power to define “proficiency” on city tests.

Jesse Rauch, executive director of the State Board, said that members welcome discussion about their role in the process of approving new cut scores. “Ultimately, what is most important is that the process be open and transparent; this time, the process of selecting cut scores was neither open nor transparent,” Rauch said in a statement.

Council member David Grosso (I-At Large) agreed. OSSE explained its decision only in response to inquiries, Grosso said, and that “gives the appearance that there is something to hide, that you did something wrong.”

“This is an opportunity for you to fix what you’ve done in the past,” he said, urging officials to send written explanations of their decision to every school and family. “In the end, parents need to know what’s going on.”