Having committed a brief article on Stern to a reference book, I find that this is such detail as I could disinter on her education:
'Educated at Notting Hill High School, she travelled in Germany and Switzerland before spending two years at the Academy of Dramatic Art'. And she comments at various points in her 'ragbag memoirs' about having picked up all sorts of random information hither and yon, some of which turned out to be wrong.