Effective Intervention to Address Disruptive Behavior

It is Ms. Dawson's second year of teaching. Things have gone fairly well during the first few weeks of the school year. She encountered only sporadic behavior issues and was able to deal with them with minimal disruptions. Recently, a new student, Devin, joined the class. Devin often teases his classmates and, occasionally, becomes physically aggressive toward them. Devin frequently makes rude comments while Ms. Dawson is teaching. Ms. Dawson tries to ignore much of this behavior, but occasionally argues with Devin when frustration sets in. The other students often laugh at Devin's behavior, and when Ms. Dawson asks him to leave the classroom, he often refuses. Ms. Dawson has found herself admonishing Devin more and more and has noticed that other students, who were previously compliant, have begun to engage in the same behavior. Ms. Dawson is not happy about the atmosphere that Devin is creating in her classroom. She has tried some of the behavior interventions she learned last year, but they are not working. She wonders what else she can do to stop Devin's behavior.
Discussion:
Based upon the variables surrounding Devin's behavior - the antecedents and consequences, hypothesize the probable function of Devin's behavior and provide a rationale for your choice.
Why do you think Ms. Dawson's initial efforts to address the problem (ignoring, admonishing, behavior interventions used for other students) failed to reduce the target behavior?
Discuss some indirect and direct assessment approaches Ms. Dawson could use to gather information that would inform the design of a more effective intervention to address Devin's disruptive behavior?