I like that you used anglo-saxons as the group to point out here. In fact many of us don't come from that background. Some of us do; I am mutt enough that Russian heebism and Irish-Englishness are both a part of my DNA. But how does that play out in childhood and adolescence, how does family figure it out? That's all different. For a teacher or any setting (for that matter) to assume a King Arthurian connection is ridiculous. In America (in particular) immigration is far to complicated and convoluded to assume race or ethnicity based on skin color.
But we do, all the time.
You totes need to read that book. Me too.