Fifty Baltimore schools are so dilapidated or underused that they should be closed or rebuilt, according to a new report that also identified $2.45 billion in school infrastructure needs across the city. The findings, released Tuesday, were used by school officials to launch a 10-year campaign to bring the system's buildings up to 21st-century standards.

The exhaustive, yearlong assessment of the system's 182 campuses rated the system's overall infrastructure — as well as 69 percent of the schools — as "very poor."

The assessment, which included a review of everything from roofs to handrails, also found that more than a third of the school system's available space was going unused — though it costs millions to maintain. Overall, the report found, the system's infrastructure fails to support quality educational programs.

City schools CEO Andrés Alonso released the results of the study at Northwood Elementary School, which was built in 1950 and is one of the schools in the worst condition.

The "Jacobs Report" — named for the Jacobs Project Management Co. — will serve as a guide for several critical decisions regarding school life spans. Those decisions will begin to unfold this week, as school officials begin a series of meetings with affected neighborhoods.

Mayor Stephanie Rawlings-Blake joined Alonso in calling on state and local leaders to use the report as a blueprint for transforming the district's buildings.

Alonso said that while the report paints a "bleak picture" of city facilities, it details the barriers to providing a quality education. "It severely impacts teaching and learning," he said, "making it a moral undertaking rather than a practical one."

The city schools facilities campaign started in 2010, when a study from the American Civil Liberties Union showed a $2.8 billion need. Later, a citywide campaign called "Transform Baltimore" grew to encompass more than 50 organizations.

This spring, Alonso asked state lawmakers to commit to paying the city $32 million annually for a financing plan that would have allowed him to borrow $1.2 billion in bonds — four times more than the city's current borrowing authority — to rebuild the system in 10 years. That would have addressed some of the school system's needs.

The proposal was championed by the ACLU and others but was rejected by state lawmakers who felt that the plan wasn't fully fleshed out, relied heavily on debt, and at the time, appeared to vary from a plan being backed by the mayor.

Now, armed with the most exhaustive inventory of schools in recent history, Alonso is preparing to go back before the General Assembly in 2013 to pitch the plan again.

"The bottom line for me is not about the condition of the schools," Alonso said. "It's what kind of settings are we going to need in order to give our students the best possible chance to succeed, in a world where the standards are becoming more rigorous, and where the gap between the kinds of setting for more [advantaged] kids and the kinds of settings for students in urban public schools is growing."

Rawlings-Blake said that while she was a proud public school parent, she "continued to be embarrassed by the conditions of our schools."

She also used the platform to sign into law a controversial bottle tax, the only new revenue stream to emerge to help pay for school construction. It is expected to generate nearly $10 million annually, and allow the system to float up to $300 million in bonds.

The report and the new law "represent a philosophy of what it takes to address decades of underfunding, neglect, and avoidance of hard decisions," Rawlings-Blake said.

As opponents of the bottle tax watched in the crowd — including Councilman Carl Stokes, who attempted to defeat the measure — Rawlings-Blake pointed out that students mattered more than influential lobbyists. She also addressed critics who propose plans with no funding, adding, "We can't say we want something without making tough decisions to make it happen."

Advocates, who have put political pressure on city leaders to develop a viable plan for school facilities, lauded the report as a first step.

The report "is a beacon of light for where we ought to be going in the city," said Bishop Douglas Miles, co-chair of the Baltimoreans United in Leadership Development, an interfaith group that has joined with other groups to campaign for better school facilities.

But leaders drove home a fact that at least 50 communities will confront in the next three months: Schools will have to close.