Continuity mistake: Mr. Butler returned the paper Lucas wrote ("A Defense of Iago"), but it is back in his home office when he uses it to highlight words in it that were also in the paper he believed Lucas substituted in his application to fill a professorship position. (00:35:37)
Suggested correction: After watching the movie on a larger screen, it appears Lucas may have left his "B+" report on his desk in the classroom - a black cover page can be seen vertical to his desk and behind the seat in front. This means that Mr. Butler had the opportunity to take the report home again. [00:26:33].