For many people, the opportunity to access and engage in education is an expectation that is widely accepted. For people with disabilities and additional educational needs, such expectations have developed as a result of systemic change in the field of education over the current and past centuries. Inclusive practices, attitudes and approaches are continually evolving to meet current social pressures and needs. In fact, the United Nations 2030 Agenda for Sustainable Development (United Nations 2015). Transforming our world: The 2030 Agenda for Sustainable Development prioritises inclusive education. Teachers are responsible for implementing an inclusive approach to education, and research has focused on the attributes of successful inclusive teachers. Research has found that the attitudes of inservice and pre-service teachers have a considerable bearing on the implementation of inclusive practices, and yet it has been reported that only a minority of secondary teachers could be described as inclusive. Research studies have suggested that ongoing professional development for trained teachers and a greater emphasis on training for inclusive education for pre-service teachers would improve competencies and attitudes towards inclusive education. Secondary teachers and pre-service secondary teachers face unique challenges in implementing inclusive education, with a considerable emphasis placed on curriculum, performance and standardised results. It is not the purpose of this chapter to debate whether inclusion is beneficial for students with disabilities or additional support needs, although this debate exists in many places. Rather, the purpose of this chapter is to consider the development of inclusion as an evolving concept and to examine the impact of pre-service secondary teacher attitudes and training to implement inclusive practices in the mainstream classroom.