The Chicago Board of Education voted Wednesday to close 50 schools and programs, an ambitious plan that has sparked protests and lawsuits and could help define -- for better or worse -- Mayor Rahm Emanuel's term in office.

City officials say the closings are necessary because of falling school enrollment and as part of their efforts to improve the city's struggling education system.

"The only consideration for us today is to do exactly what is right for the children," schools CEO Barbara Byrd-Bennett said before the board's vote.

Critics have blasted Emanuel, the former White House chief of staff, and Byrd-Bennett, saying the closings disproportionately affect minority neighborhoods and will endanger children who may have to cross gang boundaries to get to a new school.

They protested during the board's meeting Wednesday and sent busloads of parents, teachers and students to Springfield to lobby lawmakers to approve a moratorium on the closings. Chicago Teachers Union President Karen Lewis called it "a day of mourning" for the children of Chicago.

She also pledged to start a voter registration drive in an attempt to register 200,000 new voters before the 2015 municipal elections -- when Emanuel will be up for re-election -- and to raise funds to support candidates for mayor, city council and statewide office.

"We know that we may not win every seat we intend to target but with research, polling, money and people power we can win some of them," Lewis said.

The board -- which is appointed by Emanuel -- voted to spare some schools that were targeted for closure in March. Many experts say it is the largest number of closings at any one time by any school district in recent memory.

The mayor said Tuesday he believes closing the schools is the right thing to do, and that possible blowback from voters wasn't a factor in his decisions.

"I will absorb the political consequence so our children have a better future," Emanuel said. "If I was to shrink from something the city has discussed for over a decade about what it needed to do ... because it was politically too tough, but then watch another generation of children drop out or fail in their reading and math, I don't want to hold this job."

Chicago is among several major U.S. cities, including Philadelphia, Washington and Detroit to use mass school closures to reduce costs and offset declining enrollment. Detroit has closed more than 130 schools since 2005, including more than 40 in 2010 alone.

The school closings are the second major issue pitting Emanuel against the Chicago Teachers Union. The group's 26,000 members went on strike early in the school year, partly over the school district's demand for longer school days, idling students for a week.

Emanuel and Byrd-Bennett say the district's financial and educational struggles call for drastic action. They say the nation's third-largest school district is facing a deficit of about $1 billion and that too many Chicago Public Schools buildings are half-empty because of a population drop in some city neighborhoods. They've also pledged students will be moved to schools that are performing better academically.

CPS says it has 403,000 students in a system that has seats for more than 500,000. The closures include one high school program; the rest are elementary schools, serving students up to eighth grade.

Alderman Jason Ervin, whose West Side ward includes several schools slated for closure, fears the closings could further destabilize the area. He said many area residents have grown frustrated because they feel the decision about which schools to close was made months ago, despite weeks of additional hearings and community meetings.

But he was less certain what impact, if any, it could have on Emanuel's political future.

"He's the mayor. I'm the alderman. We still have to work together," Ervin said. "People will make those decisions when the time comes."