Can a headteacher shout at the parent of one his students?

No, a headteacher should not shout at a parent. While a headteacher has a responsibility to maintain order and address concerns, shouting is unprofessional, unproductive, and can be considered bullying or harassment. Effective communication involves calm discussion and respectful dialogue, even when dealing with difficult situations. Shouting escalates conflict and damages the relationship between the school and the parent, hindering cooperation which is crucial for the child's well-being.