This study describes the work of one high school team in designing, developing, supporting, and field-testing a new course to support numeracy and general learning skills for a particularly diverse population of students. The rationale, curriculum design, and pilot implementation of the course are situated in existing curriculum structures and recent research around best practices in mathematics teaching and learning, particularly with respect to vulnerable students. The study sought to explore the role and responsibilities of the course designer and teacher, as well as her perception of the challenges and benefits of a custom-designed course for this group of students. The results suggested that the crucial role of the classroom teacher in supporting students emotionally when implementing the intended curriculum for vulnerable students cannot be underscored enough. For such students, teacher-student relationships appeared to be the most important factor in student success, far eclipsing other factors.