Schools may be well-placed to identify signs of mental health (MH) problems in children; however, there has been little research into how school-based screening and intervention initiatives should be delivered. One-to-one in-depth interviews were carried out with 15 practitioners that support children's MH within primary school settings. Data were analysed with template analysis. We explored practitioners' perceptions of a school-based screening/intervention programme for childhood MH problems and views about potential barriers to uptake. Three themes were identified. First, practitioners described feeling overwhelmed by the volume of children requiring support and the limited capacity of their service. Second, practitioners identified potential barriers to engagement in a school screening/intervention programme, including familial concerns about stigma. Finally, practitioners were optimistic that a screening/intervention programme could have positive effects for children who might otherwise not be identified as potentially benefitting from support. This study highlights that a primary school-based screening/intervention programme designed in partnership with stakeholders would be well received by practitioners supporting MH within school settings.