I disagree. I think it actually shows great confidence and great self image to disclose your stuttering. People end up being impressed because it shows that you're not hiding yourself. It also makes things LESS awkward because there's no elephant in the room. I'm not saying that you should disclose to every single person or to every single clients, but it does way more good than bad. Besides, OP is in high school. He definitely should tell his teachers so they know.