In "The Breakfast Club", principal Vernon believes that the kids have turned on him and have became more arrogant. He fails to acknowledge his own faults as a principal. This can be explained by:

self-serving bias

Explanation:

Self-serving bias refers to the propensity to associate adverse circumstances with external causes, whereas favorable events are the cause of personal credit. In other words, people attribute success to personal qualities, while they blame outside sources for their failures. As a result, in "The Breakfast Club," Vernon cannot accept his wrongdoing as a principal and holds the children responsible for being arrogant and misbehaving.