I tell the child "I can't understand you when you talk to me using that voice" over and over until the child calms themself down and delivers their grievance at

I tell the child "I can't understand you when you talk to me using that voice" over and over until the child calms themself down and delivers their grievance at a normal volume. Then I explain why things are the way they are and the tantrum re-erupts (usually) so we repeat the process two or three times. This technique requires a huge amount of patience, though, and it certainly doesn't get you to school on time.