Who is the author of Harcourt 5th grade science edition?

Answer 1

Most likely one of Harcourt's lackeys, which means its really Harcourt.

Beware the textbook publishers. They're the one's writing entire curriculums based around NCLB's standardized tests.

Answer 2

Textbooks like that do not have authors. Most likely you are looking for an author for a bibliography? You have to use the primary editor as the name, and then add ed. (for editor) and et al (meaning and all the rest because these textbooks have more than one or five or ten)