WASHINGTON — A group of investors announced plans yesterday to buy Sallie Mae, taking the nation's largest student lender private in a $25 billion deal that comes as some regulators call for tougher standards and lower federal subsidies for the $85 billion college loan industry.

Private-equity firm J.C. Flowers & Co. and three other investors will pay $60 per share for the Reston, Va.-based SLM Corp., commonly referred to as Sallie Mae. The sale price represents a nearly 50 percent premium for Sallie Mae's previously sagging stock before takeover rumors emerged late last week.

SLM shares traded up more than 17 percent on the New York Stock Exchange after the buyout was announced yesterday.

J.C. Flowers and private-equity firm Friedman Fleischer & Lowe will invest $4.4 billion and own 50.2 percent of the company. Bank of America and JPMorgan Chase each will invest $2.2 billion and each will own 24.9 percent. The buyers will also provide Sallie Mae with $200 billion in backup financing.

John Oros, a managing director at J.C. Flowers, said the firm was drawn by Sallie Mae's stock price, which had fallen to around $40 per share before takeover talks began. The investors also weren't deterred by the brewing troubles for lenders and the prospect of a clampdown on the industry by lawmakers.

"We think Sallie Mae is a great company and a great business, and appropriate regulation will sort itself out in a way that will make this an attractive transaction for us," Oros said.

Sallie Mae is by far the largest school lender, originating $23.4 billion in student loans last year, many of them federally subsidized such as widely used Stafford loans. The company has recently expanded into other areas of lending, such as debt collection and 529 college savings plans.

But it has also been subject to greater attention from lawmakers and regulators currently probing ties between lenders and college officials who guide students toward specific lenders for their loans.

Last week, Sallie Mae settled with New York Attorney General Andrew Cuomo over the company's business practices, agreeing to pay $2 million to a student loan education fund. It will also no longer pay travel and entertainment expenses for university officials or send its employees to work for free in campus financial aid offices.

Citibank also agreed to a similar $2 million payment, and yesterday, San Francisco-based Education Finance Partners settled an investigation by Cuomo and agreed to pay $2.5 million.

Some Democratic lawmakers and even President Bush have threatened to cut federal subsidies to student lenders. Rep. George Miller, D-Calif., chairman of the House Education and Labor Committee, said last week that the buyout raised concerns about transparency at Sallie Mae.

Miller said in a statement yesterday that given "the checkered past of Sallie Mae," he and Congress would be interested "in learning more about how this new ownership will change their operations, and whether this is truly in the best interests of student borrowers and families who are working extremely hard to pay these loans back."