FAIRY-TALE ENDING? The tug o' war over Renaissance Learning, whose products include Accelerated Reader and Accelerated Math, ended on Tuesday when shareholders accepted a $455 million bid from European private equity firm, Permira Fund, even when Minn.-based Plato Learning dangled out an extra $41 million. A federal judge in Wisconsin (when Renaissance is incorporated) had to rule that the company was allowed to take the lower bid: more typically, boards exercise their fiduciary responsibility to shareholders by accepting the biggest check. One way to sidestep the problem: the founders, who owned 69% of the company, gave other shareholders a $16.60 price per share; they took a mere $15 a share. (Even so, Plato's bid amounted to an across-the-board $16.90 a share.) No word on future plans from Permira, which maintains a diverse, international portfolio of about two dozen investments.