Are boys from Mars and girls from Venus? Should secondary schooling be segregated by sex? The recent history of education is of violent swings from one extreme of fashion to another, and it looks as though the co-educational pendulum is on the move once more.
Debate has been raging in America, partly thanks to campaigning by Leonard Sax, a paediatrician convinced that boys' attention problems are caused by education not being tailored to their needs. The Bush administration has also expressed interest in creating more single-sex schools.
But the US situation is very different: America has little recent history of single-sex state schooling, and laws barring sex discrimination in education have made experimentation difficult.
Now the brawl has arrived on our shores, with both sides of the debate piling in for a conference at Wellington college, a boys' public school that will admit girls from September.
As ever, the debate is more low-key here. Single-sex state schools were common until the 1960s, since when numbers have dropped from nearly 2,500 to around 400. Most are fiercely supported by parents: many, especially girls' schools, top exam tables.
Independent schools, traditionally single-sex, are going mixed more slowly.
Girls' schools, in particular, extol their benefits during the turbulent years of puberty, including freedom to take "unfeminine" subjects and experience leadership. Meanwhile, some mixed comps are going the other way, experimenting with segregated lessons to see if results improve.
So three cheers for our home-grown educational guru Professor Alan Smithers, who has taken a long, cool look at all the research and concluded that there is no discernible educational benefit from single-sex schooling.
Nor is there a benefit from co-education. In other words: take your choice (he chose single-sex for his own girls). It is a sane, and (dare we say it?) very British solution: parents should choose what is best for their child. Increasingly, they can choose on the grounds of faith: perhaps choice should also be available on the grounds of gender?