Meet Wally and Carolyn, two young people who will go on a date Friday night.

They exist on film - a mental hygiene film from the years following the Second World War. The term "mental hygiene" is a way of describing instructional films with titles like "Dating Dos and Don'ts", "Mind Your Manners," "Are You Popular?" and "Narcotics: Pit of Despair." Topics also include posture, highway safety, and juvenile delinquency.

These films were shown in classrooms across America as tools of social engineering, made to reshape the values and attitudes of students in the late 1940s and 50s. They generally were wrapped up in simple and tidy 10-minute packages.

More than 3,000 of these films were made over nearly three decades. Now, fewer than half of them survive, and often only one or two battered prints. Most schools and libraries dumped the bulky films when video came in. The copies that remain are scattered among university and museum archives or private collectors.

A still photograph taken from a "mental hygiene" film.

Our tour guide through this funny, fascinating and largely forgotten world of "mental hygiene" films is Ken Smith. He's the author of a book called "Mental Hygiene: Classroom Films, 1945-1970."