Hello! I was drawn to your post title because my 4 yo son is out of control right now (I'm 9 months preggo, so it's just about to get worse...that's another conversation). Anyway, he will scream a lot, and I do just let him do it in his room. I actually don't claim to know much about raising my own son, as I am going crazy trying to figure out what to do with him. But I was a behavioral therapist for 3 years and ignoring a behavior to put it on what they call "extinction" is actually a really good method for getting kids to stop doing stuff you don't like. Typically if they are misbehaving over and over again, it's because they are getting something reinforcing out of whatever you are doing as a reaction. Even if it's taking away privileges, yelling, time out, etc. and it seems counter-intuitive - if he keeps screaming and you keep covering his mouth, he might like the attention from you and do it again. I recommend putting him in his room and ignoring until he is done. Then give him positive attention when he stops. I hope it works!