Career Education Corp. on Thursday announced that it would close 23 of 90 campuses and lay off 900 employees to cope with declining revenue and enrollment. The for-profit chain has been hit hard by what a company official called "new market realities," and has seen its total and new student numbers dip by roughly 22 percent compared to last year. It also reported an operating loss of $110 million for the year through October. The company is taking the "difficult step" of downsizing as part of a plan for a strategic turnaround as a "simplified and more nimble organization," said Steven H. Lesnik, its president and CEO, in a written statement. Career Education Corp. is also facing scrutiny from its accreditors.