The College Board, which administers the SAT, in their official guide for scorers explains:
"Writers may make errors in facts or information that do not affect the quality of their essays. For example, a writer may state 'The American Revolution began in 1842' or ' "Anna Karenina," a play by the French author Joseph Conrad, was a very upbeat literary work.' " (Actually, that's 1775; a novel by the Russian Leo Tolstoy; and poor Anna hurls herself under a train.) No matter. "You are scoring the writing, and not the correctness of facts."