It's hard to keep a good company down.

Twice now, I've pointed to depressed valuations on for-profit educator Apollo Group (NASDAQ:APOL) as tempting, but not quite tempting enough. First in October 2004, and a year later in October 2005, when the price neared a short-term nadir, I explained the reasons for the stock's fall and expressed interest in buying. Sadly, neither time did I bite. In each case, the depressed share price was followed in short order by a regained strength, after which it began flying higher once again.

Today, though, the stock is once again trading around where I first highlighted it as approaching a buyable level. So with the stock once again high off some recent lows, investors are looking with hope toward Thursday morning's earnings release and wondering whether the stock can fly higher still. Analysts are optimistic that it can. They project that Apollo will report 19% sales growth and 21% growth in earnings for its first fiscal quarter of 2006.

Future expectations are similarly high. The belief is that Apollo will repeat its 19% earnings growth in fiscal Q2 but boost earnings by 23% year over year this time. Even as growth slows further along fiscal 2006, it's thought that the company can still achieve 18% earnings growth for this full fiscal year and 19% more in fiscal 2007.

That's all well and good, but what Fools need to focus in on is not just the company's earnings growth but also the "quality" of those earnings -- specifically, whether the company's "accounting profits" are backed up by "cash profits," or free cash flow. Last year, when Apollo experienced declining year-over-year FCF generation, it nonetheless generated more cash ($462 million) than generally accepted accounting principles permitted it to report as net earnings ($445 million.) But that was a narrower difference than we saw in fiscal 2004, and this apparently arose from the company's letting its accounts receivable get a bit out of hand; A/R rose 38% year-over-year, despite revenues rising just 25%.

So tomorrow, we'll want to check back in on Apollo and confirm that it has its A/R situation back under control and free cash flowing in abundance. If it does -- and of course, if it feeds the Wall Street beast the requisite assurances on forward guidance -- that just might signal the "all clear" for Apollo to fly once more.

For recent Foolishness on Apollo, read:

Fool contributor Rich Smith has no position, long or short, in Apollo Group.