Random Riddle: Sally’s French

Sally has four classes, Science, Math, English Language Arts, and History. She had a test in every class, and wanted to have some fun, so she did all of her tests in French. When she received her tests back, only one teacher could understand her work. If none of Sally’s teachers spoke French, which teacher was able to understand the test and how did they understand it?
 
Random Riddle: Sally's French