Look out McGraw-Hill. Activist hedge fund Jana Partners and the Ontario Teachers’ Pension Plan Board have bought 5.2% of the publishing, investment analysis and TV station company — and say that they may try to break it up. The investors reported in SEC filings today that they have “no present plan or proposal” for the company run by CEO Terry McGraw. But they plan to talk to McGraw-Hill’s directors, shareholders, and others about changes “to improve shareholder value.” That could include changes in McGraw-Hill’s “business, operations, management, board composition and representation, corporate structure, strategy and future plans,” they say. The news contributed to a 5.5% increase in McGraw-Hill’s share price in after-hours trading. The company is already trying to reorient itself. Last year it sold BusinessWeek magazine to Bloomberg, and it recently put its TV station group on the block. The company’s best-known properties include Standard & Poor’s and J.D. Powers Associates.