Theorists, yes, but why "left wing"?The loopy 'whole language' idea is part of the 'pure discovery' model of teaching (or more accurately, not teaching) which has only ever been supported by the left wing theorists. Pure discovery didn't work when they tried it in the 1970s, it didn't work when they reheated it in the 1980s and it's failing our schools now.
I'm not saying that the right wing 'back to basics' focus pushed by the Howard government is completely right either, but it's a hell of a lot closer to the mark than pure discovery and it was a necessary correction to a declining system. The ALP governments since then (located firmly in the centre, not on the left) recognised this and supported more rational policies on learning with their engagement in the culture wars largely limited to the teaching of history, but there will be a whole generation of illiterate graduates before the teachers trained only to 'facilitate' discovery instead of actually teaching get pensioned off.
There are many things the left get right in the world of education, but the 'whole language' model is not one of them.