When managing a student's poor behavior having them engage in a task to lodge a complaint is helpful. Have a policy in place for lodging complaints, have them write down the complaint. When they speak to you about the complaint you take notes. I think these are good suggestions to allow the student to think critically about their complaint and calm them down. Also, listen to what they are saying and ask for their idea of a resolution, that will make them feel heard and is a good starting point to moving toard a resolution.
