The vocational math teachers at a vocational secondary school lack the adequate skills needed to be effective in math classrooms. The vocational teachers who teach math at the local vocational school have been identified as noncertified teachers based on their certification with the state department of education. The purpose of this project study was to determine the best professional development sessions needed to improve the instructional practice of untrained math teachers at the school. Their work is critical to the academic and career development of students. The social development theory of Vygotsky, which states that social interaction has an effect on individuals' growth and development, was the conceptual framework for this study. The research question focused on teachers' perception of the best approach to improve instructional strategies of vocational teachers in math. A qualitative case-study design was used to collect data from 8 teachers using interviews at the local vocational school. Data were analyzed and coded based on common themes. Member checking and triangulation of the data were used to ensure accuracy and credibility. The findings of this study showed that teachers at the study site need professional development, specifically a district policy ensuring that vocational math teachers receive professional development training, common planning time, participation in professional learning communities, and support in understanding the math objectives they are expected to teach to ensure their continuous improvement. This project may influence social change by spurring administrators to provide additional training to vocational educators, which may improve the quality of teachers' level of instruction and subsequent student outcomes. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://bibliotheek.ehb.be:2222/en-US/products/dissertations/individuals.shtml.]