Create a safe setting, limit the number of adults involved, give personal space, show open, accepting body language, use peaceful tone and verbal interactions.

An Escalated Adult Cannot Control an Escalated Student
Create a safe setting, limit the number of adults involved, give personal space, show open, accepting body language, use peaceful tone and verbal interactions, communicate simply and directly, identify their wants and needs, reassure the student and frame an outcome, coach them to take responsibility for their behavior, find agreement.
How to article
Both the student and the teacher need to use appropriate body language and verbal interactions.
This goes back to modeling expected behavior. If the teacher is modeling negative behavior then the student will follow.
“To start, getting down on the child’s level can avoid the child feeling as if the teacher is looming over them. Body posture should remain comfortable and relaxed. Gestures such as crossing arms and pointing fingers should be avoided for the most part. Movements should be kept slow, deliberate, and non-confrontational” .