A physics professor was telling me yesterday that her daughter was having trouble understanding real and virtual images formed by lenses.  That was until she showed her a real image being formed on a sheet of paper by a (spectacle?) lens.[1]  The curriculum (which you all must follow or you will be sent to the salt mines!) only included ray tracing.

And this was at a “good” school.  It seems that our teachers are being frustrated by the production of all these “Jobs for Little Stalins” (of which Britain has so many) that our educational bureaucracy has contrived over the years.
[1] I have had to make a correction here: at first I thought the teacher made a five-minute “Great Escape” from the jam-packed curriculum, and did the demonstration.