The aim of the present article is to seek changes in teachers' beliefs and attitudes towards heterogeneity at school after their participation in a two-year training programme. Research sample were 78 teachers with Greek national identity, who work at schools in Thrace, an area of north Greece where the ethnic identity of an important part of pupils is Turkish. The research showed that the teachers' participation in the above training encouraged their feeling professionally efficient and satisfied from their work at the above-mentioned schools and impacted on their former beliefs and attitudes when dealing with ethnic cultural differences and the general heterogeneity of the school class. (Contains 4 figures.)