Tomorrow's Magic — Pamela F. Service

It's 500 years after the nuclear holocaust that devastated the earth's population and left the few survivors dealing with unending winter. At their remote British boarding school, Wellington Jones and Heather McKenna
have a lot in common. Both are misfits trying to avoid attention, and both are fascinated by Earl, a tall, calm, older boy with no recollection of his past, but a remarkable knack for showing up when he is needed most.

When a blow to the head brings Earl's memory back, he claims that he is actually Merlin . . . a 2000-year-old wizard.

Originally published in two volumes in the mid-1980s, Pamela F. Service's creative, futuristic spin on the Camelot legend will appeal to Arthurian purists and fantasy lovers alike.