Mathematics teachers, mathematics department heads, curriculum leaders, and administrators from 11 schools in four school boards from Toronto, Ontario, Canada, participated in a project to improve the teaching and learning in grade 9 mathematics classrooms. In each of these schools, an implementation team was created, so that at least three teachers from every school could collaborate, in order to improve learning outcomes of their students. This article reports on the challenges identified by teachers when they taught grade 9 applied mathematics. Teachers' views of challenges fell into five main layers: (a) teacher professional development and pedagogical skills, (b) student learning needs, (c) settlement issues and families' social and economic background, (d) administrative difficulties and resources, and (e) curricular issues. These challenges were complex and interconnected, demanding special remedial efforts by the administration and teachers. By reflecting on the challenges and practices, these teachers made a long-term strategy to engage in professional development activities to better understand their students' learning needs and to improve their achievement in provincial tests.