I'd love the breakdown between SAHM, works from home mum and WOHM.
It stands to reason that a woman currently working full time will be better placed to guide their daughter into good career choices than one whose been out of the working world for ~20 years, and this may result in a faster, more targeted career progression for the daughter.
What would be interesting is if the trend hold true for the daughters of those people who work from home, where home is their employment, say childminders etc. That would suggest this is far more than an obvious cause-and-effect link.
I suspect, though, whatever it turns out to be, it'll all end up being yet another stick to beat women with about their parenting choices.
I third that comment about schools (and LEA's for that matter!) needing to wake up, though - it's be lovely if DD's primary got the message sometime soon, although they have just missed their Outstanding from Ofsted purely on the basis of it, so there's hope!