In 16 mm, with a sputtering projector.
Each of these movies was shown at least three or four times in my early school years, but I hadn't seen any of them since until I thought of searching online. Looking for "Clown" required a bit of creative Google searching (it couldn't have been called something easy to find like "Purple Fossils From Venus," of course). But I did find them, actually without too much trouble, and the only one I haven't been able to watch is "One Little Indian"--we don't have the right plug-in at the minute. But at least I know that it exists and that I didn't make it up!
If you went to school before everything was shown on VCRs, what semi-educational films do you remember seeing?
Richard Balducci's "Clown"--description here (look under Drama), download here.
"Le Ballon Rouge / The Red Balloon." Uploaded on You-tube in four parts, first part here.
Grant Munro's "One Little Indian," made for Canada's National Film Board. Description and photo here, but I suddenly can't even find the page with the excerpt. Maybe you'll need to find a creaky 16mm projector to watch it.