Having skipped its pension contributions for many years, Chicago is supposed to start tripling them in another year under state law. But the school district has drained its reserves. And it cannot easily turn to the local taxpayers because of a cap on property taxes. Borrowing the money would be difficult and expensive as well, because of a credit downgrade this summer. One of the few remaining choices would be to make deep cuts in other services.

Like Chicago, many cities and school districts now face pension pressure after reducing their contributions in recent years to save money. Among the funds for different types of workers, teachers’ plans tend to be shortchanged more often, according to research done by the Center for Retirement Research at Boston College for The New York Times.

The reasons are unclear, but in many states — California, New Jersey, Rhode Island and Illinois, among others — pension contributions must be set by state legislators every year. And since teachers’ pension costs are blended with other education spending, lawmakers sometimes decide to withhold money from pensions to allow more direct state spending on the schools. The teachers’ pension fund for the State of Illinois is in even worse shape than the Chicago teachers’ fund.

What many Chicago residents may not realize is that their school district also has been paying $130 million a year to cover most of the pension contributions required of the teachers, a practice known as a “pickup,” which became a flash point last year in the collective bargaining battle in Wisconsin. Wisconsin’s public workers have agreed to make their own contributions, as a concession.

Officials in Chicago know they have a pension problem, even though it was not front and center in the strike. Mayor Rahm Emanuel focused on trying to improve the quality of public education, with a longer school day and more meaningful teacher evaluations. The Chicago Teachers’ Union, meanwhile, was intent on reinstating a 4 percent pay increase, and protecting those who are laid off when failing schools are closed.