Santa Ana-based Corinthian Colleges Inc. saw its stock price plunge more than 21% today after it reported a drop in earnings for the March quarter.

The dip dragged Corinthian’s market value down to $258.1 million.

Profit for the post-secondary education company fell 75% to $4.1 million in the quarter ended in March. That compares with $16.1 million in profit in the same period a year earlier.

Quarterly revenue was $424.1 million, down 7%.

Investors had sent Corinthian’s stock up more than 36% three months ago when the company released a relatively positive report for the December quarter. It posted net income of $1.8 million then, a turnaround from a year-earlier loss of $163.7 million. Its market value at that time was about $350 million.

Chairman and Chief Executive Jack Massimino said the company has cut operating expenses by about $150 million over the past year and a half. The company has also sold off some of the 100 or so campuses it runs in the U.S. and Canada as parts of various brands.

“We completed the sale (and) lease-back of five Heald campuses, and we are in the process of selling or [closing] seven Everest campuses,” Massimino said.

New enrollment for the Corinthian schools rose 1.8% to 29,427, while total number of students fell 4.2% to 96,631.

Massimino said Corinthian is “introducing several new diploma programs across our ground schools” to help students obtain the equivalent of a high school diploma.