[sparky_75]

There's another interval here from 1990- yet again there doesn't seem to be any sign of a non-sync frame roll.

www.youtube.com 

Yet again the supporting materials caption looks like a slide or physical caption- there's even loads of dust all over it. Does seem a bit odd these were still in use so late, can't find too many examples of physical slides and captions still being used for this sort of thing after around 1988-ish.

Have a bit of first hand knowledge of this...
The C4 "Roto" was entirely computer generated - designed by Central TVs in house promotions team.

The "supporting items" image is likely to be a transfer of a 35mm slide. Many of these were still in use fro years - but had been transferred to Tape as individual slide scans - some with all the dust/faded images and crap on them.
Invariably, the slides would be produced by the programme maker.
With ATV / Central responsible for networking Schools Programmes from Birmingham - chances are they just sat on the slides as they were'nt specific to content of the programme, but only specific to the series. (Saves making up more slides)

Many of the programmes shown - even after the move to Channel 4 were made on 16mm film; in the case of Central programmes - some were slightly re-edited each term (esp in the case of Stop, Look Listen and Good Health) with new prints struck for transmission.
The Film Unit at Central closed in 1990 - and most of their schools programmes ended up being made on Tape thereafter.

Incidentally, both versions of the Schools Clock used on ITV were mechanical, and aired using a caption scanner camera.
The programme caption would be replaced between programmes, the captions being white text on black background.
There were also 35mm versions of this too - without the captions - which could be used by regions who had opted out of Network programming to show their own (Westward / HTV Wales etc) - programmes with the film clocks attached are easy to spot, as the clock judders and jumps as it counts dow!
By 1985 - the clock was sourced from a Videotape transfer.