Public relations for the Stand Up for Students campaign, a citizen initiative to increase public school funding by creating a 3 percent surtax on income above $200,000, has been taken over by the Knight Canney Group, the campaign announced Monday. The hiring of the PR firm, whose past clients include Angus King and Eliot Cutler, is a signal that the funding question on this November’s general election ballot will be the subject of an intense campaign.