As my third-grade school year (circa late 70s) began to wind down, my teacher decided to eat up half a school day treating the class to a showing of the classic 1939 film The Wizard of Oz. Not on VHS (we didn't have that technology yet.) Not even on 16mm film. No, this presentation was in film-strip format.
Imagine a seemingly never-ending store of stills from the film we'd all seen annually on television, each frame punctuated by an ear-stabbing alarm-clock BEEP! sounding every few seconds, even during the music segments. "Somewhere, over the rainbow..." BEEP! "...Way up high...And the dreams that you dream of..." BEEP! "...Once in a lullaby."
What should have been a welcome reprieve from the regularly scheduled classroom curriculum had, by hour three, turned into something of an endurance test. A few kids tried to lay their heads down on their desks, but even sleep was no escape, because BEEP!
A much more pleasant grade-school film-strip memory was my music class presentation of this 1963 illustrated interpretation of the Camille Saint-Saens classical piece Danse Macabre (illustrator is Harold Dexter Hoopes), screen capped below in its entirety from a transfer posted to YouTube by lostmediaarchive.
I remember breathlessly describing the viewing experience to my Dad that same night, who suggested (mistakenly, but a good guess) that it may have been the Night On Bald Mountain segment from Disney's Fantasia.