Nearly 1,200 Chicago teachers and staff are being laid off due to declining enrollment in one of the nation's largest districts, Chicago Public Schools (CPS) officials said last week.

CPS officials said 1,150 employees received pink slips, and among them 550 were teachers. The other 600 staffers included teacher assistants, clerks and part-time security guards.

Chicago Teachers Union (CTU) president Karen Lewis slammed the city's mayor, former White House chief of staff Rahm Emanuel, and its board of education, calling the decision "yet another brutal attack on public education in Chicago".

Last year, the school district adopted a per-pupil funding model, which ties a school's budget to the number of students enrolled. As a result, a school’s annual budget reflects increases or decreases in enrollment. The amount a school receives per student does not change.

Teachers affected by the layoffs can reapply to work in the district as there are 1,780 teaching vacancies, 1,420 of which are full-time positions, CPS said in a statement. In past years, approximately 60% of displaced teachers have found positions with in the district, it said.

CPS said that roughly one-third of district-run schools would lose some teachers. Details of which school had been affected were not immediately known.

In the last couple of years more than 5,000 teachers and other employees have been laid off, CTU staff coordinator Jackson Potter said. In July of last year, CPS officials announced 2,000 layoffs, and more than half of them teachers, according to the Chicago Tribune. These cuts were made to help alleviate the city's budget deficit.

Potter said charter schools were diverting students from public schools, bringing enrollment numbers down. He said this left schools to make difficult decisions, such as "choosing between a librarian and a core math or English teacher".

Potter added that the most recent layoffs come in addition to more than 100 teachers and staffers who lost their jobs at three academically under-performing schools. The city's board of education slated the three schools for "turnaround", a controversial policy which aims to raise a school's performance by letting go nearly all employees are replacing them with new staff.

In a statement, Lewis, the union president, also criticised Mayor Emanuel for going after President Barack Obama's library and George Lucas' Star Wars museum.

"Do we want Star Wars museums or public, neighborhood schools? Do we want presidential libraries or librarians for every child?" Lewis said.