For years, nearly seven in 10 New York City middle-schoolers have failed to meet state standards in math and English, but many have graduated to high school anyway.

Yesterday, Mayor Bloomberg announced that his administration is planning to bring that era of consequence free failure to an end at public middle schools, an expansion of his sweeping plan to end “social promotion.” Struggling seventh-graders will be given intensive extra help, and those who score at the lowest level on the end-of-the-year standardized math and English exams will be held at that grade level.

Mr. Bloomberg announced the new policy at a three-day conference for New York City middle-school principals.

The first, and most controversial, installment of the mayor’s attack on social promotion began in March 2004, when Mr. Bloomberg forced a policy through the Panel for Educational Policy that required third-graders at least approach grade-level standards before being promoted to the fourth grade. The second installment, announced last fall, extended the policy to the fifth grade.

According to Department of Education statistics, the intensive interventions associated with the policy have reduced the number of third- and fifth grade students failing the exams. Among third-graders, the only grade level where numbers are available, fewer students were held back the year the policy was implemented than the year before.

“Maintaining the status quo is simply not an option. It doesn’t do anyone any favors to send unprepared students up the line to the next grade. Those days are over, I think we all agree,” Mr. Bloomberg said.

Mr. Bloomberg said his administration chose seventh grade as its next target for improvement because “seventh grade represents our last, best chance to prepare students for the demands of high school work.” He said students who flounder in seventh grade are likely to fail in high school as well, and are much more likely than their peers to drop out of school altogether. Also, Mr. Bloomberg said, seventh grade is a kind of “launching pad” for high school since high school admissions are based on students’ seventh-grade scores.

The administration is pouring $40 million into the new initiative. That money will pay for summer school for failing seventh-graders and a Saturday school for struggling seventh-graders modeled on the Saturday Preparatory Academy that served fifth-graders this past year. Some money will also go directly to middle-school principals, to pay for specialists and professional development. Reaction to the mayor’s newest education policy was mixed – though the tone was far more positive than it was two years ago.

The president of the United Federation of Teachers, which for two years has been locked in a contract dispute with the city, praised the new proposal.

“We support the mayor’s plan to end social promotion in the seventh grade as a good way to build on past successes and help better prepare our middle school children for high school,” Randi Weingarten said.

The president of the principals union, Jill Levy, said the plan is “another step in the right direction.”

The chairwoman of the City Council’s Committee on Education, Eva Moskowitz, was less optimistic. When it comes to middle school, she said, “Retention is hardly the solution. We need a Marshall Plan for middle schools.”

She said the money would be better spent aiding the education of the city’s youngest children.

Education officials said yesterday that they were not focusing on middle schools at the expense of early-childhood education. The deputy chancellor for teaching and learning, Carmen Farina, said she was meeting yesterday with experts in early-childhood intervention strategies. “We’ve tapped every expert out there who appears to know something about this so we can pluck their brains,” she said.

Some of the mayor’s Democratic political rivals quickly jumped on Mr. Bloomberg’s announcement. “Testing alone isn’t a positive plan for giving kids a quality education,” the City Council speaker, Gifford Miller, said. “The right way to end social promotion is making sure that every child in our city is in a classroom that isn’t overcrowded, has a quality teacher, is safe, and provides strong after-school opportunities.”

The Democratic front-runner in the mayoral race, Fernando Ferrer, said Mr. Bloomberg’s policy fails to acknowledge low graduation rates, even though both Mr. Bloomberg and his schools chancellor, Joel Klein, said the policy was aimed at preparing students for high school so that they would be less likely to drop out.

“Our dropout rate is a citywide shame,” he said. “It’s a crisis that threatens half a generation of New York children. That’s why I presented a plan last week to address this crisis head-on. I challenge Mike Bloomberg to do the same.” The Panel for Educational Policy is expected to vote on the policy at next month’s meeting.