Actually not just sex ed, but lots of science/health shows, popular culture, videos, heck even advertising, had clips/images of (human) sperm attempting to fertilize an egg - and sometimes succeeding - so advancing to the next chapter on fetal develoment :). (The specific clip that triggered my memory on this is in the opening scenes of Peter Gabriel’s 1986 ‘Sledgehammer’ video - the blue/grey backlit sperm by ova, right before the blood stream).
Suddenly I had one a ‘Duh’ moments - the creators of these videos/images probably weren’t jamming '70s style video equipment up a fallopian tube and waiting around, hoping for the best - I think in general they must have been extracting ova, getting some sperm, adding those to a solution filled petri dish and filming the results - and if a sperm successful penetrated the egg and all, that would be the technical definition of In-Vitro Fertilization, wouldn’t it (ignoring the rather more difficult ‘successfully implantation of the zygote in a womb’ part, of course)?
Am I correct about this? Is that (in general) how these images were filmed (I remember lots of different ones around that time), and if so did people even care back then (well, OK, the Catholic Church for example) since the fertilized ovum would probably be discarded (3rd option - they used some other mammal ova & sperm - could non-biology students tell the difference between human gametes and say pig or rabbit ones?).
My initial guess is that they weren’t human.
That is certainly a possiblity, as I mentioned in my OP. I probably wouldn’t be able to tell the difference - since apparently pig sperm is compatible w/ some human genes to start with:
Can’t really think of any good search terms of the ‘making of sperm and ova images’ (which on Google gets you mostly info on IVF, BTW) 
couldn’t find anything from the 60’s or 70’s, but here’s In the Beginning from 1937.
“the spermatazoa, shed by the male during mating, appear like tiny little fish…or shall we say tadpoles?”