The adventure of the three students

Professor Hilton was reviewing passage of Greek that was going to be translated during an examination. He left his study for a while and after he came back, he saw the keys to the study in the lock. Someone had apparently copied a part of the translation and there were some clear evidences. The professor turned to Holmes and asked for his help. Can some of the students that were about to take the examination have copied the text? Will Holmes solve the case before the exam the next day? "The Adventure of the Three Students" is a part of "The Return of Sherlock Holmes".