The British Film Institute has released a double DVD anthology of British sex education films from 1917 through 1973 called The Joy of Sex Education.

The earliest films warned teenagers of the dangers of
unwanted pregnancy, venereal disease and doing nothing "of which you
would be ashamed to tell your mother or your sister".

Many of the films were released in the years around the Second
World War, when the Government was keen to protect the health of
troops, often separated from their wives and families.

But the
films do not move as easily from innocence to explicit material as
might be expected, said Katy McGahan, from the British Film Institute,
who put the films together.

She said: "What I expected to see a
very neat progression from a euphemistic, talking around the subject,
approach in the 1910s and 1920s that you would expect to a much more
liberalised and explicit approach with the onset of the so-called
sexual revolution in the 1970s.

"Although that was the case to
some extent many of the early films were much more progressive in their
attitude than later films".

You can check out Katy McGahan and psychologist Dr. Petra Boynton discussing the films in an interesting BBC podcast as well as more footage from the collection.

The film collection has Guardian blogger Peter Bradshaw riveted:

There
can’t be many new DVD releases of short film anthologies which are
unstintingly riveting all the way through. But here’s one. For the past
couple of days, I have been glued to the BFI’s incredible collection The Joy of Sex Education,
which is a compendium of sex education films from 1917 to 1973. They
have a weird similarity to old-fashioned stag films, not merely because
of explicit content, but because they are designed to be watched in a
semi-clandestine world: created not for cinemas or television but for a
private clientele in church halls and classrooms and family planning
clinics.

Some of these films are genuinely horrifying. The
brutally entitled Don’t Be Like Brenda (1973) is an eight-minute
lecture to young women, telling them not to be sexually promiscuous
like the film’s hapless heroine – although heaven knows, the
promiscuity hinted at here is tragically modest. Poor Brenda goes all
the way with a boy who does not marry her. The film is stunningly
without any useful educational content on contraception and makes it
entirely clear that the woman, not the man, is to blame. The film even
makes her poor unwanted child suffer from a heart defect, so that no
one wants to adopt the poor little thing – just to hammer the point
home. Katy McGahan’s excellent programme note on this film (in the
DVD’s accompanying booklet) doesn’t mention it, but the caddish male in
the film is played by Richard Morant: many of the film’s target
audience would have seen him, two years previously, playing the evil
Flashman in the BBC’s teatime adaptation of Tom Brown’s Schooldays.

…

The undoubted masterpiece of this double-DVD set is Martin Cole’s
23-minute Growing Up from 1971. Now, this begins with some pretty ripe
statements about the differences between the sexes, with some blather
about how the softer female sex stays home nesting and the questing
males are "usually more inventive and creative". But the film boldly
shows film of real people – not coy line drawings – in a concerted
attempt to show the realities of where (gasp!) babies come from.
Remarkably, it even shows film of real people – a man and then a young
woman – masturbating. This clear, frank and in fact rather dignified
film got Cole tonnes of hate mail, encouraged by the tabloid press.