It involved the state’s decision to create short, predictable exams and to release them publicly soon after they were given, making coaching easy and depriving test creators of a key tool: the ability to insert in each test questions for future exams. Next year, for the first time, the tests will not be released publicly.

It involved a national push for numbers-based accountability, begun under President George W. Bush and reinforced by President Obama. And it involved a mayor’s full embrace of testing as he sought to make his mark on the city, and then to get re-elected.

“They just kept upping the stakes with the scores, putting more pressure on the schools but not really looking at what it all means,” said Pedro Noguera, an education professor at New York University who has worked with the city’s Department of Education to help improve struggling schools.

New York has been a national model for how to carry out education reform, so its sudden decline in passing rates may be seen as a cautionary tale. The turnaround has also been a blow to Mayor Michael R. Bloomberg and his chancellor, Joel I. Klein, who despite warnings that a laserlike focus on raising scores could make them less and less reliable, lashed almost every aspect of its school system to them. Schools were graded on how much their scores rose and threatened with being closed if they did not. The scores dictated which students were promoted or left back, and which teachers and principals would receive bonuses.

Even now, the city believes that the way it uses the tests is valid. The mayor and the chancellor have forcefully defended their students’ performance, noting that even after the changes this year, student scores are still better than they were in 2002. They have argued that their students’ progress is more important than the change in the passing rate, and that years of gains cannot be washed away because of a decision in Albany to require more correct answers from every student this year.