I have seen few spoofed versions of this film or it's parts until I found this original.
Apparently it's from early 1970's and it's aimed to help out teaching sex ed for disable - the title is from the ebaumsworld.com - not quite sure if it's original (I'm still trying to find that out as well as the release year).
And yes, the word "trainables" is used in this film itself...

This film covers anatomy, periods, wet dreams, masturbation...

"We must teach to those with serious disabilities that hinder their learning to live as successfully as possibly with other people. This includes their sexual behaviour. But rather than teach which is somewhat difficult, it becomes a training situation with as much explanations as they can absorb."

"Sex education should also involve instructing them how to recognise and avoid sexual exploitation. Trainables are particularly vulnerable because the common characteristic of trust, lack of judgement and the desire of affection."

Sex education for trainables - lenght 7:01
(ebaum doesnt like embedding, so just a link)


Here's one short spoof version made from the masturbation scene.
lenght 1:12