With the release of the results of the important fourth- and eighth-grade English exams just days away, New York policy-makers and educators cautiously predicted higher scores and scrambled to figure out which factors might cause averages to swing up or down.

The state and city education departments closely guard and analyze the data, which will help determine which schools are failing under the federal No Child Left Behind law – and might shape voters’ views of Mayor Bloomberg’s education record. Testing experts said, meanwhile, that a range of factors could affect exam outcomes, including the population of the test-takers, the level of preparation, and the difficulty of the tests.

The experts said that it would be impossible to judge how challenging the test questions were until the results are released, but that the other two factors – population and preparation – could provide indications of what the data might show.

This year’s fourth-graders went through the first year of Mr. Bloomberg’s plan to end the “social promotion” of failing third-graders. As of last October, 3,012 third-graders had been held back – fewer than the 3,105 who had been held back the year before the policy was implemented.

Although the numbers don’t show that struggling students were barred from the fourth grade and kept from taking the exam in English Language Arts, they do show that the students who were promoted were better prepared. Last year, 7,263 fourth-graders who scored at the lowest level, 1, on the third-grade standardized tests were promoted to the fourth grade. This year, only 2,522 level-1 third graders were promoted. The director of the center for research on teaching and learning at New York University, Robert Tobias, said a change in population as a result of the promotion policy could boost averages.

Mr. Tobias said another population change that might increase scores stems from a new statewide emphasis on granting exam waivers to English-language learners who have been in the country for four or five years. The waivers enable those students to take the state English as a Second Language Achievement Test instead of the English Language Arts exam.

The teachers union has said 3,000 additional English-language learners took advantage of the policy. The city Department of Education says only 900 additional students secured waivers. Even if every one of them had taken the English Language Arts Exam and scored at the lowest level, it would have a minimal impact on the average scores. The state Education Department says the waiver policy is not new.

The president of the United Federation of Teachers, Randi Weingarten, said another variable that might boost test scores is that teachers have now been using the city’s new curriculum in language arts for two years and are more adept at it than they were last year.

“Teachers really do try to figure out how to use everything that’s thrown at them,” she said. “So you have the second-year uptick.”

She also said there has been an “excessive amount of test prep,” which she said might boost fourth-graders’ scores but probably wouldn’t have much impact on eighth-graders’ scores.

“Our sense is that the New York City score will go up about 10 points,” Ms. Weingarten said, referring to the fourth-grade average. “Some of it is for reasons like the test prep and the [English Language Learners] being exempt. Some of it is because this is the second year that you use a curriculum, people get a sense of what to do, and you get a bump. And some of it is because of the fantastic work that teachers do.”

An education historian, Diane Ravitch, also predicted scores would rise.

“From what I’ve heard from many principals and teachers, there’s been a lot of time devoted to test prep,” she said. “I assume the test-prep strategy will show a short-term gain.”

The department acknowledges it has used academic intervention programs – including the Wilson Reading Program, Read 180, Lexia, Great Leaps, Voyager, and others – to help target individual students’ learning problems. Education officials contend, however, that those differ from test preparation.

One person who wasn’t so optimistic about the scores was the city’s public advocate, Betsy Gotbaum.

“Teaching to the test will undoubtedly be a big factor, but it doesn’t have a lasting effect,” she said. “Last summer, failing third-graders were taught to the test, and as a result, most of them got promoted to the fourth grade. But this year, there are just as many fourth graders in jeopardy of failing as there were last year. Teaching to the test is the ultimate quick fix. It does nothing to prepare students for the work they will face in the years ahead. It’s just social promotion in disguise.”

Last year, the teachers union predicted the fourth-grade average would rise by five percentage points. Instead, it fell by almost three.