This is the 1st in a series (a trilogy) read in school around 1992-1993 (7th grade). The plot is a boy and a girl in the 20th century finding a teen, Art, and discovering that he is actually King Arthur. Art gets hurt toward the end of the book and they have to go Avalon to save him from the bad guy.
Stump the Bookseller
New format, same book stumper solving.
Could it be “The Forever King” by Molly Cochran and Warren Murray? from Amazon.com–“Arthur Blessing is no ordinary ten-year-old. The Grail is his by chance, this time, but the power to keep it–a power as ancient as time itself–is his by right.”
sounds like Susan Coopers “The Dark Is Rising” series!!