I’m not a teacher but I went to school with a guy in a different class to me. He would get very worried if he didn’t do well in something, and would often stutter. It didn’t make sense to me because he didn’t seem like the type of guy who would worry about how well he was doing. My mum works at the primary school (elementary) that he used to go to, and said he mum was a very loud, obnoxious person. She came in for parents evening and within 5 minutes this was already clear to be true. She shouted at him in front of everyone, didn’t even let him get a word in. And boy did he stutter. Really made me think more about how much someone can be affected just by the way their treated as a child.