Guess you are looking for factual stuff, but Arthurian legends (and there are many) are a possibility. For a high school student, the Jack Whyte series is really good (and actually is historical fiction, it doesn't have magic in it like most Arthur/Merlin stories do). And as a 13 year old I LOVED the Mary Stewart series. Which does have a small amount of magic but is still amazing.
D20 suggests:
Catherine Called Birdie
Anna of Byzantium
The Squire's Tale
She does, however, say that in her opinion medieval is not as interesting without dragons
