This continues to confuse Americans. I have recently seen it once more used to denote an elaborate afternoon tea. For such an occasion, the food provided usually includes cake and other items, in addition to bread and jam.
High Tea in the UK is an evening meal for children, usually served at about 5 or 5:30. This includes a simple main course, such as sardines on toast, and is usually anything but fancy. The idea is to feed the young children and then send them to bed, so that the grown-ups can enjoy a leisurely dinner at (say) 7:30 or 8 pm.