​Is the University of Phoenix flaming out?

The University of Phoenix is predicting brighter days ahead, although it's not clear when or if they'll arrive.

The largest U.S. for-profit educator has lost more than half of its students during the past five years, ending its fiscal second quarter with 213,800 enrolled students compared with 458,600 in early 2010. Year-over-year enrollment slid 14.6 percent.

The reason for the drop, according to parent company Apollo Education Group (APOL) Chairman Greg Cappelli, is the online educator is refocusing on attracting students "better prepared for our programs."

Cappelli spoke to investors after the online educator on Wednesday reported fiscal second-quarter results and cut its annual revenue forecast, with its shares falling about 30 percent. Apollo said it lost $36.1 million in the most recent quarter, compared with a profit of $12.2 million in the year-earlier period, while revenue declined 14 percent.

The problems won't be over anytime soon, as Apollo is predicting a continued decline in enrollment. Chief financial officer Brian Swartz told investors on the conference call that the company expects to end its fiscal 2015 with about 200,000 students, or a 6.5 percent dip from current levels.

"Frankly we are not finished," Cappelli told investors. "We have the fixtures in places but the plumbing is not all hooked up, right, meaning we are developing a plan, college by college. It takes people, it takes strategy and processes; it takes the programs which are being developed and put in place."

The school has rebuilt its programs and methods for attracting and retaining students, now providing a trial period that allows would-be enrollees test the waters before signing up. That's caused some would-be students to realize college might not be a good fit, although it's helped strengthen the university in other aspects, said Apollo chief of staff Mark Brenner.

"While we've seen some decline in enrollment, the median debt for our students is in line with the median debt nationally. Our default rates are now less than the national average," Brenner told CBS MoneyWatch.

At the same time, some national trends are also taking a toll on enrollment, such as a strengthening economy that's creating job opportunities that are pulling some students back into the workforce.

While the University of Phoenix faces competition from both traditional colleges and online rivals, the entire sector of for-profit colleges has come under fire in recent years. A 2012 Senate report found that more than half of students who enrolled in 2008-09 left without a degree or diploma. Students who graduate from for-profit colleges carry an average of $39,950 in debt, or 43 percent higher than graduates of other types of four-year colleges, the Project on Student Debt found in a 2013 report.

And then there's the case of Corinthian Colleges, a for-profit rival of University of Phoenix, which crumbled last year amid lawsuits and slumping enrollment. The Consumer Financial Protection Bureau, for one, sued the institution last year, alleging that it "lured tens of thousands of students to take out private loans to cover expensive tuition costs by advertising bogus job prospects and career services."

While Corinthian still exists in some form today -- a student loan guaranty agency bought about half of the institution earlier this year -- the lawsuits opened a critical eye on the world of for-profit colleges. At the same time, the issue of student debt at for-profit colleges gained a human face with a group called the Corinthian 15, a group of former Corinthian students, declared a "debt strike," refusing to pay back their loans in protest over being lured into what they called "debt trap."