The ever-volatile secondary-education sector faced a storm of stimulus Thursday, bullish and bearish.

Two companies, Hoffman Estates, Ill.-based

Career Education

(CECO) - Get Report

and Santa Ana, Calif.-based

Corinthian Colleges

(COCO)

, were falling in premarket trading after the

Financial Times

said Career Education was the focus of a federal grand jury investigation.

The newspaper said Justice Department investigators are considering whether the company should face criminal charges related to claims of record-keeping malfeasance at some of its subsidiary schools. Career Education was falling $3.22, or 10.4%, to $27.79, extending a plunge that began when the stock was above $70 in mid-June.

Career Education's biggest thorn has been a purported class-action suit in which 12 former employees allege the company inflated enrollment records in an effort to collect more student loan reimbursement than it deserved. The company has denied the allegations repeatedly. Thursday's story in the

FT

said agents in the U.S. attorney's office for Chicago are being assisted by the Education Department's inspector general and the enforcement division of the U.S. Postal Service.

Corinthian, which fetched a split-adjusted $36.19 on April 19 before a slew of earnings warnings and legal entanglements sent it spiraling, was down 27 cents, or 2.3%, to $11.11 in Thursday's premarket.

Meanwhile, Phoenix-based

Apollo Group

(APOL)

, which runs more than 200 schools and is the largest provider of higher education in the country, said after the bell Wednesday that first-quarter revenue will be $529 million to $532 million, while full-year revenue should be $2.285 billion to $2.288 billion.

Analysts had been expecting $529 million in the first quarter and $2.267 billion in the year. The company expects to earn 56 cents a share in the quarter and $2.40 a share in the year, excluding items, both well above estimates.

The stock was recently up $2.21, or 3%, to $75.55 on Instinet.