The first picture is a black and white still showing the catastrophic chemistry lesson in which Willow Rosenberg, who is secretly a witch (Alyson Hannigan, extreme right), accidentally turns a visiting health and safety inspector (Joyce Grenfall, left) into a toad, witnessed by Miss Fritton, headmistress (Alistair Sim, right).
The second picture is a small colour still, apparently a publicity shot which was not used. It shows Buffy (centre rear) talking to the school boxing team while Flash Harry (George Cole, centre front) explains the fine art of taking a dive.
[Note - No guarantee whatever that either scene will be in the story...]
Later - I've found a much better picture to use for Willow, and have redone the first picture accordingly.