The system Mr. Cuomo wants to revamp dates only from 2010, the year New York and many other states, lured by the Obama administration’s offer of financial rewards in its Race to the Top competition, moved to new evaluation systems. The idea was to replace methods that were largely based on principals’ observations, and in which almost every teacher was rated satisfactory, with systems that would use student test scores and differentiate better teachers from worse ones. In New York, teachers who were rated ineffective two years in a row could be fired, even if they had tenure.

Under the current law, zero to 40 percent of teachers’ ratings, depending on several factors including their districts and grade levels, is linked to students’ progress on the exams. A majority of the ratings are still based on subjective measures like principals’ evaluations and parent or student surveys.

Contrary to the hopes of those who expected the new system to identify a significant portion of struggling teachers, 96 percent of teachers last year were rated either effective or highly effective. (The governor exaggerated in his op-ed article, if only slightly.) In many cases it was the subjective part of the evaluation that was responsible for the high scores.

“I can believe that there are districts, high-performing districts, where they may not have any ineffective teachers — that’s wonderful,” said Sandi Jacobs, the vice president and managing director for state policy at the National Council on Teacher Quality, which supports more stringent evaluation methods. “But the fact that there isn’t a single teacher in the district who, whether because she’s new or for whatever reason, is still not at where we’re ready to call her proficient — where we’re ready to say day in and day out this is an effective teacher — that seems not to line up with what we know about student results.”

The challenges of giving honest evaluations are not unique to education. James N. Baron, a professor at the Yale School of Management, said that in the corporate world, it was widely known that supervisors were biased toward rating their employees highly.

“One obvious reason is that people don’t particularly like to give negative evaluations,” Professor Baron said.