The corporate ratings of student lender SLM Corp. or Sallie Mae (SLM) was downgraded by Fitch Ratings yesterday. The outlook assigned was negative. The ratings downgrade reflects the agency’s concern about the company’s business model. Fitch expects the company to continue to shift to a fee-for-service business model with its subsidiary Sallie Mae Bank originating higher-risk private education loans.   Fitch downgraded the long-term issuer default and senior debt ratings to "BBB-" from "BBB", while preferred stock was downgraded to "BB" from "BB+". The short-term issuer default rating and short-term debt ratings were affirmed at "F3". About $34.4 billion of debt and preferred stock is affected by these actions.   To restore the $92 billion student loan market, the House Education committee approved a legislation, which closes the Federal Family Education Loan Program and shifts most of the student lending into the Education Department's Direct Loan program. ...