Faced with rising calls for a strategy to rescue the city’s struggling schools, Mayor Bill de Blasio announced a $150 million plan on Monday to flood more than 90 of the city’s lowest-ranked schools with supports for students and staffers.

But in an effort to preempt critics who have accused his administration of giving failing schools a pass, de Blasio made clear that these 94 schools will face consequences if they do not meet certain targets. Even as he rebuked the previous administration for “casually” shuttering schools that were never given adequate assistance, de Balsio said the city will “close any schools that don’t measure up” after three years of intensive support.

“We will move heaven and earth to help them succeed,” de Blasio said during a speech Monday morning in an East Harlem high school, “but we will not wait forever.”

The new plan, dubbed “School Renewal,” turns the city into perhaps the nation’s most prominent test case of the theory that school improvement must extend beyond the classroom. Following the so-called community schools model, the city will bring physical and mental health practitioners, guidance counselors, adult literacy teachers, and a host of other service providers into these schools. They will also add an extra hour of tutoring to the school day and receive money for new after-school seats, summer programs, and more additional teacher training.

The plan also highlights de Blasio’s sharp departure from former Mayor Michael Bloomberg’s reliance on competition and consequences to spur school improvement.

De Blasio allies who had opposed his predecessor’s approach embraced the new tact. Some 70 lawmakers, union and business leaders, and advocates offered their endorsements of the plan in a release sent out by City Hall on Monday.

But critics of the administration pounced on the plan, attacking it as limited and weak. They noted that it leaves out many low-performing schools, it does not specify the exact targets schools must meet, and puts off the most serious sanctions for several years.

“The mayor’s plan is too small, too slow, and too timid,” said Jeremiah Kittredge, CEO of Families for Excellent Schools, a pro-charter school advocacy group that has been critical of de Blasio’s education policies.

State education department officials apparently shared some of those concerns: A spokesman said Monday that Commissioner John King may force the city to “take additional actions in these schools” next year if he decides they are not making enough progress.

“There are times when struggling schools need significant structural change in order for meaningful progress to occur,” said the spokesman, Dennis Tompkins.

Chancellor Carmen Fariña forcefully defended the plan and the administration’s shift towards collaboration and support, telling reporters Monday that if her predecessors’ more aggressive approach had worked, “I wouldn’t be sitting here now talking about how we’re going to turn the schools around.”

“We want to prove the skeptics wrong,” she added.

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The announcement comes 10 months into de Blasio’s term and well into the school year, after educators and advocates have for months urged the city to outline a clear plan for the city’s many low-performing schools. Some educators have said the delay will make it harder to enact major changes this year, and the principal of one long-struggling school who recently resigned said he had lost faith in the city to help his school.

The city was required to submit improvement plans to the state for roughly 250 low-ranked schools this summer, but officials asked for a months-long extension to file final versions. The state gave the city until this Friday to turn them in. However, over the weekend, the city asked for another extension through the end of the year, which the state is currently considering, according to Tompkins.

Even as officials finalize those plans, the city will start to enact parts of the new turnaround program, de Blasio said. Fariña is currently evaluating the principals of the targeted schools, and their teachers will soon get new training. The schools will be sent new guidance counselors this spring, he added.

Other key components will launch later. For example, the schools will not offer the extra support services for students and their families until next year, when they will be sent teams of seasoned principals and teachers to act as coaches.

As the program rolls out over time, schools will be expected to meet certain goals. The only requirement this year is for schools to create individual improvement plans by the spring. Next year, they must hit various targets, including higher attendance, and by 2017 they must show growth in students’ academic performance. Officials said the goals will vary by school, and will take into account student test scores, educators’ efforts to work with families, and the quality of teacher training, among other measures.

Principals hoping to revamp their schools’ academics by removing poor-performing teachers will have to go through the normal evaluation and hearing process, officials said. To ease that process, superintendents will make sure principals properly document instances of teacher misconduct and incompetence, they added.

The 94 schools include some the state has identified as poor performing, and all rank among the bottom quarter in the city as measured by test scores and graduation rates.

The $150 million covers the first two years of the program, and comes from state struggling-school funds and money freed up through cost-savings in the education department budget, officials said. Funding has not yet been secured for the program’s third year, the officials added. De Blasio said more state money is needed to turn around more schools.

“We will need Albany to step up and help us,” he said.

The city’s plan encompasses the School Achievement Initiative, which sent coaches into 23 of the city’s lowest-performing schools this year. It is separate from the $52 million de Blasio set aside earlier this year to create 40 community schools, officials said.

Making community schools the centerpiece of the city’s vision for improving the system is likely to resurface debates about the effectiveness of non-academic services at boosting student achievement. (De Blasio has visited Cincinnati to observe their community schools model, though many of its schools are still struggling to improve their academic performance.)

De Blasio’s school-improvement plan also evokes the Chancellor’s District, a support program in the late 90s and early 2000s for the city’s lowest-ranked schools, though officials said the new program will tailor supports to each school’s needs. Schools in the Chancellor’s District made short-term gains in fourth-grade reading scores but no changes in eighth-grade scores.

The Coalition School for Social Change, where de Blasio made his speech Monday, will be part of the new program. Principal John Sullivan said he hopes to use the new resources to add more social workers, medical and dental services, and help for students who are behind in credits.

“I think the plan will mean a tremendous amount of support for my school community,” he said.