Paraprofessionals are increasingly being hired to support students with special needs in schools and are key implementers of behavior interventions for students. However, research is limited on how paraprofessionals perceive the management of student behavior. Using a mixed-methods design approach, the current investigation assesses paraprofessionals' perceptions of common student behavior problems in elementary school classrooms. Results indicate coached paraprofessionals had a greater likelihood of reporting operationally defined behavior concerns than those in a control group. A qualitative constant comparative method of analysis of paraprofessionals' behavior reports revealed themes of disruptive academic behaviors (off task, peer/verbal interactions, physical interference), aggressive behaviors (physical aggression toward people/objects, verbal aggression), noncompliance (physical/verbal refusal), and "other" behaviors (unclear/opposite or positive actions). Implications for practice and future research are discussed. [For the corresponding grantee submission, see ED608171.]