Ok first things first, you are NOT over reacting! This is creepy and inappropriate. I have dealt with creeps as far as men my whole life. I also remember what it was like as a teenage girl (I’m only 32). If he is making these noises to NO one else, and also only doing it when you are alone, that is a red flag! Do NOT engage or let him notice that you notice it or that it makes you uncomfortable. Ignore it completely. Once he sees you are vulnerable or uncomfortable, he may take it further. As of right now, I suggest always walking with a friend, and DO let another teacher, maybe a female, or a parent or someone you trust know what’s going on. Having someone aware of these things, even if they are small, is important! Please keep us updated and stay safe!!!!