08/01/2011 06:41 EDT | Updated 10/01/2011 05:12 EDT

Ontario Teachers Pension Plan Board buys stake in McGraw-Hill Cos.

NEW YORK, N.Y. - The Ontario Teachers Pension Plan Board is teaming up with activist hedge fund Jana Partners to buy a 5.2 per cent, $531 million stake in textbook publisher McGraw-Hill Cos.

Jana, a New York-based hedge fund that oversees about $3 billion, said in a securities filing Monday that the shares are undervalued and that it may take steps to boost shareholder value.

Shares of McGraw-Hill jumped $2.34, or 5.7 per cent, to $43.50 in after-hours trading on the news.

McGraw-Hill owns the financial ratings agency Standard & Poor's, educational publisher McGraw-Hill Education, Platts energy information services and J.D. Power and Associates.

The company said last month it plans to divest its broadcasting unit as it reviews its portfolio of businesses.

With $107.5 billion in assets as of December 31, 2010, the Ontario Teachers' Pension Plan is the largest single-profession pension plan in Canada.