AZ, perhaps I was wrong in making such a definitive claim. But from what I see, little boys need to stay with their mothers as long as little girls do, this may give rise to an extra year of playgroup for girls who need socializing, and as girls are ready to learn just as early as the boys are, it will not be an easy last year of playgroup for these kids who are ready to learn. Takeh, Rabbi Aisenstark has said that lechatchila kids should be home till about 5 (years old, not PM) but this isn’t the world we’re living in.
And I really don’t think we’ll get the uniform compliance needed for this to work.
And I’m very leery of social engineering. As it is the system could use more work in the chanoch l’naar department.