I believe hearing students learn from a deaf teacher as well as they do from a hearing teacher. Hearing and deaf students do cheat, you know. I have seen deaf classmates communicate through sign language during tests and quizzes when a teacher did not look.
My case was different, though. During my junior year at a private school, I had a HOH teacher, Mr. Goad. He didn't know any sign language. I couldn't remember what his medical conditions and hearing loss level were. He did wear his hearing aids. Also, His back was not straight, and he usually lifted his head up, so he can look at students or write on the board. He looked like Dr. Stephen Hawking. I did not have an interpreter. I can read his lips, and understand him most of the time, because he talked slowly, which was helpful for me. He knew that. He was extremely brilliant, and taught advanced math classes like calculus, trigonometry, statistics, and analysis. Unfortunately, the students did make fun of his appearance, and his hearing aids. He knew all about it. He stuck his guns.
One time, the class and I were working on math practice problems. Some students in the back of the class were whispering and being immature. Mr.Goad slammed his fragile hand on the desk, and barked at students," I can hear!" He pointed a finger at his hearing aids, "If you do it again, I'll kick you out." He kept reminding the class if a student caught whispering or cheating during tests/quizzes, there will be major consequences. The class felt his presence. He did watch like a hawk. I never forget his serious looks.