Half the world will do nicely
As for "shielding themselves from nasty, rude, distracting boys in order to make something of their lives", well here she may have a point. To quote her own words in the article, "even the gentlest of boys push, shove, shout and barge ahead; seem oblivious to anything around them and tie up the majority of any teacher's attention."
Given a choice between a relatively peaceful environment where one can achieve one's potential to the full, without too much distraction from immature youths and the type of co-ed situation Hilary describes, and knowing that aliens are always around in the evenings and at weekends, the majority of intelligent young women and their parents, if they have a choice at all, will opt for a single-sex school every time.
Burgess Hill School
Burgess Hill, West Sussex