A major focus in the science, technology, engineering and mathematics (STEM) public engagement sector concerns engaging with young people, typically through schools. The aims of these interventions are often to positively affect students’ aspirations towards continuing STEM education and ultimately into STEM-related careers. Most school engagement activities take the form of short one-off interventions that, while able to achieve positive outcomes, are limited in the extent to which they can have lasting impacts on aspirations. In this paper, we discuss various different emerging programmes of repeated interventions with young people, assessing what impacts can realistically be expected. Short series of interventions appear also to suffer some limitations in the types of impacts achievable. However, deeper programmes that interact with both young people and those who influence them over significant periods of time (months to years) seem to be more effective in influencing aspirations. We discuss how developing a theory of change and considering young people’s wider learning ecologies are required in enabling lasting impacts in a range of areas. Finally, we raise several sector-wide challenges to implementing and evaluating these emerging approaches.