WASHINGTON — Sallie Mae's planned $2.5 billion stock sale doesn't answer all of Wall Street's questions about the struggling student lender's future.

While some analysts see the company's financing woes as a short-term problem, others highlight serious concerns about the Reston, Va. company, such as soaring loan defaults and a potential cut in its credit rating.

Sallie Mae, formally known as SLM Corp., earlier this month lowered its earnings forecast for next year by more than 13 percent, blaming a new law that trims federal subsidies and the need to conserve cash to offset bad student loans. Then CEO Albert Lord held a contentious conference call last week in which he dismissed several analysts' questions and ended the call with an expletive.

These developments only compounded pressure on the company's stock price, which has fallen steadily since July, when a group of investors who eventually backed out of buying Sallie Mae for $25 billion first indicated the deal could be in trouble.

Shares fell $2.48, or 11 percent, to close at $19.65 on Thursday, a day after the company said it would spend $2 billion from the stock offering to settle unprofitable contracts that require it to buy back shares at above-market prices. The company's shares have plunged to their lowest price since early 2001.

Sallie disclosed in a regulatory filing Thursday that federal education officials plan to examine whether the company's billing practices complied with federal law. The company also noted a discrimination lawsuit filed against it last week in a Connecticut federal court by two women who alleged the company charged students higher prices at schools with high black and Hispanic populations. The company denies this.

Several Wall Street analysts on Thursday lowered their 2008 earnings forecasts for Sallie Mae, as per-share profits are likely to drop due to the addition of stock. But some said Sallie is likely to benefit in the long run from continued growth in the student lending market as smaller competitors retreat because of tougher business conditions.

"Long-term opportunities within student lending remain robust," Mark Sproule, an analyst with Thomas Weisel Partners, wrote in a note to clients.

Other analysts were more skeptical.

Goldman Sachs analyst James Fotheringham said in a research report Thursday that Democrats could push to diminish the role of Sallie Mae and other private companies in the student lending market. He also foresaw pitfalls if Sallie Mae's executives seek to acquire other lenders.

Credit rating agency Moody's Investors Service said last week that an ongoing review of Sallie Mae for a possible downgrade would focus on "potentially weakening" finances at the student lender. Moody's plans to complete its review by the end of January.

Lehman Brothers analyst Bruce Harting was more optimistic, saying in a research note Thursday that the offering may be large enough to raise SLM's credit rating to "A" from its current level of "BBB," two notches above junk-bond levels. A higher rating would enable the company to borrow money at a lower cost.