We just tell DS that "It's too loud, please use your inside voice. " if he doesn't stop I tell him, "that's too noisy, I'm not listening" then don't respond until he stops. If he talks I talk back but screaming gets no response.
Generally I don't like ignoring him, but any attention paid to the screaming made it 50 times worse. Every time. It took a while but he knows now that if I say it I mean it, and he stops within a minute or two.
DD2 would do that. It got to the point where I had tO put her in time out because nothing else worked. It took three days and no more screaming. She has completely stopped for the past year. In the car, I ignored her if she screamed but that was really tough. Good luck x
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