Sex Ed from 1948.

The Stork Didn't Bring You:  Obviously, it's dated -- the girls' vocabulary section has entries like 'Obstetrician' and 'Gynecologist', while there's one in the boys' section on Prostitutes ("Also called harlot, whore, or trollop.") and the author explains that homosexuality can be "corrected" by hormone injections and/or counseling -- but her attitude towards sex ed in general, as seen in the Introductory Word, is pretty wonderful.

AND it must be noted that she was super-hip -- as she says to the reader, "this is cold turkey in your own language".

(via Bookslut)