A significant number of students are living with diagnosed and undiagnosed mental health disorders such as anxiety, depression, post-traumatic stress disorder, schizophrenia and substance-use, and this number has only increased due to the COVID-19 worldwide pandemic. When students are demonstrating symptoms of languishing mental health within the classroom, it is the classroom teachers, resource teachers and counsellors who experience first-hand, the challenges that come along with this, and work to implement strategies to support these students. This qualitative study has the purpose of obtaining the perspectives of classroom and support teachers on their experiences in working with students with mental health needs and how they are addressed and supported in school-based settings that are implementing Positive Behavioural Interventions and Supports (PBIS). The data from individual interviews were analysed and coded, revealing six themes: 1) Diversity of student mental health and wellbeing in the classroom, 2) Implementation and integration of PBIS and SEL, 3) Strategies to support student mental health and wellbeing in schools, 4) Barriers and challenges in supporting student mental health and wellbeing in schools, 5) Effect of PBIS on student mental health, and 6) Impact of Covid-19 on students’ and teachers’ mental health and wellbeing. This study makes recommendations for change in current practice in schools, including the integration of PBIS and SEL, administrator support of instructional strategies that foster positive mental health, and the development of school culture that has an emphasis on collaboration and co-teaching.