The purpose of this study is to investigate beliefs of secondary school teachers on factors of effective teaching support for high ability students. The participants (Ν = 41) served in schools of Attica and participated in a structured interview process. Research items explored practices used by them for the teaching of Modern Greek Language to their students (n = 86), who later during that school year (2010) excelled in the Pan-Hellenic Exams. Also, the participants were asked about the changes that should be made in school life for the effective teaching support of high learning ability students, in general. The findings showed that participants mentioned, as supportive of high ability students' needs, mainly traditional teaching behaviors suggesting that they don’t seem to have realized differentiated teaching parameters. On the other hand, they proposed changes that should be made relating mainly to differentiation parameters such as the enrichment of the curriculum and of the teachinglearning process. Implications for the reform of the curriculum as well as the teachers’ training are discussed.