Why is it only the right that get angry about how state schools fail the poor?

Does it matter if the poor are given a bad eduction? Christine Blower, head of the National Union of Teachers, has just been on BBC1 Sunday Politics. She’s very influential (as her £155,000 pay package suggests) especially at a time when Labour policy is aligning behind NUT policy. When confronted with figures showing how the poor achieve far worse exams results than the rich, she had this to say:-