Morgan's main claim is that she is being asked to step down because she's not a Tory, and that the present Conservative-Lib Dem coalition wants to put more Tories in top quango positions. Which it probably does want to do, because after all it is a political government with a political agenda. Previous Labour governments were not exactly leaping over themselves to appoint Tories to top quangos; by the time they finally left office the vast, and largely unknown and unaccountable, quangocracy was awash with dead-beat Labour supporters. Morgan, indeed - a political person, as her present complainings make very clear - was appointed by the Coalition, presumably as a nod to the sort of political even-handedness that governments try for at the beginning of their terms.
Michael Gove has praised Sally Morgan's "fantastic" contribution to Ofsted, which we'll take on trust as to be honest I doubt whether ordinary punters, or the more directly affected teachers, could tell you what has been so fantastic about Morgan's time in office. Most Ofsted waves are made by its chief inspector - currently Michael Wilshaw, who whatever his flaws has a distinctive record as a practising educator - so Baroness Morgan's contribution has been far more under the wire. But the bottom line is that she has not been so darned good that there is an unanswerable case for keeping her on. She was a political apparatchik appointed to a political job, and she's served out her term. All her present fuss suggests is that she is yet another member of the unelected political class who doesn't want to hand over the perks of easily obtained office.