For at least the sixth straight year, principals rated more teachers as unsatisfactory.

Last year, 2,118 teachers received unsatisfactory ratings, setting them along a path that could lead to termination. That number, making up 2.7 percent of all teachers, was 16 percent higher than in 2010 and more than twice the number of U-ratings handed out five years ago. In the 2005-2006 school year, just 981 teachers received unsatisfactory ratings.

About 80 percent of the teachers who received unsatisfactory ratings were tenured, according to Department of Education data. And about a quarter — 511 — received the scarlet rating last year as well.

The numbers suggest that principals are responding to the city’s sustained push to usher more weak teachers out of the system, and the city says 86 of the U-rated teachers have already resigned, including 41 who were denied tenure. But they hardly reflect a sea change in the way that principals rate teachers.

For that, the city is counting on a new teacher evaluation system that will do away with the binary satisfactory/unsatisfactory rating choice altogether. State law now requires districts to enact evaluation systems that use student test scores as a component and sort teachers into four categories from “highly effective” down to “ineffective.”

After the city instituted a similar evaluation rubric last year solely teachers up for tenure, the number of teachers receiving tenure fell dramatically. Nearly 40 percent of teachers up for tenure in 2011 had their probationary periods extended. And a Department of Education official said last month that a pilot version of the new system in about 20 schools yielded an 18 percent “ineffective” rating rate.

The new evaluation system is supposed to go into effect in September. But some components require union approval and union officials say that no negotiations are yet underway.

The vast majority of teachers, more than 97 percent, received satisfactory ratings last year, and in a statement, UFT President Michael Mulgrew focused on them.

“The number of U-ratings confirms that principals know what the UFT and parents already know: We have one of the best workforces in the country,” he said.

More than 40 percent received the low rating because of their instructional practices. Principals cited poor attendance in 15 percent of the ratings and classroom management problems in another 15 percent.