As word spread yesterday about the city’s retroactive grade-inflation policy for public high school students who took Advanced Placement courses, the chairwoman of the City Council’s Committee on Education called the system’s implementation “beyond stupid,” and the leader of the teachers union said it is “a perfect example of how not to do public policy.”

The New York Sun reported yesterday that the Department of Education went into the citywide grading computer network in late October and changed the way students’ grade-point averages were calculated, adding 10% to each Advanced Placement grade that students earned since they started ninth grade. The new grading system jumbled class ranks at schools around the city.

“Deciding in the middle of the school year – not only in the middle of the school year but in the middle of the night – to change the formula upon which grade-point average is calculated and therefore admissions to college, etc., is beyond stupid and unbelievable,” Council Member Eva Moskowitz said. “Anybody who has taught or run a school knows you’ve got to tell people what the policy is in advance of the high stakes. Everybody has to know what the rules of the game are.”

Ms. Moskowitz said it’s premature to judge the policy because she doesn’t know much about it or the theory behind it. She said she plans to write to the chancellor demanding an explanation of the policy and reasoning behind it.

“I need to understand exactly what the problem they’re trying to solve is,” she said. “What I know is a bad idea is to do it mid-year, mid-course.”

The president of the United Federation of Teachers, Randi Weingarten, said she can see why the department would want to reward students who enroll in the hardest classes, but she said the department made a mistake when it implemented the policy.

“There were no hearings about it. There’s no sense about is this a good public position or not, is this a good public policy or not. Even the kids who would have benefited from it don’t know about it,” she said. “It’s just a perfect example of how not to do public policy.”

The Manhattan borough president, C. Virginia Fields, also offered a critique of the decision-making process.

“It is troubling to me that choices made three years ago are now being retroactively rewarded or punished without warning,” Ms. Fields, who is a possible 2005 mayoral candidate, said. “I am sure that many students might have taken advantage of this grading policy had they known it would have bumped them up one full grade point. Unfortunately, noncommunication is a pattern at Tweed.”

Public figures who frequently criticize the administration aren’t the only ones upset by the sudden policy shift imposed by Tweed. Principals and parents at some of the top city high schools are also reeling from the decision, which principals discovered when they logged into the grading system and found that class ranks had shifted dramatically.

A member of Stuyvesant High School’s school leadership team said there were “major differences” in class rank under the new system. He said the leadership team unanimously passed a resolution to use non-weighted GPAs for the purpose of calculating class rank, especially this year, but also in the future.

Despite the rising tide of criticism, the education department defended its decision. “It’s not a matter of imposing,” the deputy chancellor for teaching and learning, Carmen Farina, told the Sun yesterday. “It’s a matter of treating all kids in the city equally and fairly. The AP courses are standardized courses. The tests are standardized tests. So how can you say that in one school it means X and in another school it means Y?”

She said the system was created at the request of regional leaders and principals who wanted to give children an incentive to take AP classes.

Ms. Farina also said criticisms about the retroactivity of the policy are unfounded. “Whenever we would make the change – be it now, next year or two years from now – it would always be retroactive to something,” she said, “because you can’t have something now without having a past. So it’s not that we’re penalizing. We’re actually rewarding the kids who did this.”

She said “the principals in each school” should deal with the impact of the policy on class rank and its impact on who becomes valedictorian. She offered no suggestions of how they could do that.