To her credit, Cho was a Ravenclaw, and that pretty much automatically meant she was smarter than at least three-quarters of the rest of Hogwarts. Their first study date together went far better than Harry could have imagined; she was a genius at Charms and helped him with his essay on Banishing Charms Professor Flitwick had given him to complete. In return, Harry helped her with her Defence Against the Dark Arts assignment about the more powerful Shield Charms. Cho herself admitted that Defence was her weakest subject by far, and Harry was pleased that he was able to help her out.