How did ';flash cards';make their entry into the educational school system?

Did the process mimick a human trait? There are some flash card pictures still in my memory that I would rather not have to keep, but unlike the papper ones, these can not be thrown away. only when I am able to write of them do their immage fade.How did ';flash cards';make their entry into the educational school system?
well, i'd imagine flip cards started with the stone age kids going to school and writing crap on stone tablets with chisels and $hit, then its just went from there...im drunkHow did ';flash cards';make their entry into the educational school system?
When the battery is dead it goes off does not fade.


Every where flash is going like lightning.
To drill drill drill drill DRILL information into or little robot childerns heads. About the time of the cold war begining.

motor oil