Students' social, emotional, and behavioural (SEB) needs are associated with their academics and school behaviours, and teachers are in proximal roles to address students' needs. However, it is unclear how teacher-student understanding of SEB needs relate to students' academic achievement and behaviours. Based on 264 ninth-grade student-teacher dyads from one American semi-urban high school, teacher-student levels of SEB agreement were assessed and compared with students' grade point averages, school attendance, and number of disciplinary referrals. Findings indicate that the degree of common agreement about SEB needs ranges from 48% (engagement) to 87% (bullying). Further, teacher-student agreement about externalising and bullying behaviours relates to students' GPA and attendance. Agreement about an array of social skills also predicts students' office disciplinary referrals. Understanding the level of agreement between teachers and students is critical in informing teacher professional development and SEB-related classroom instruction.