A qualitative study of was conducted to have an insight about public school teachers' use of instructional applications and their daily practices. The specific objective of this study was, to explore how teachers apply instructional theories, methodologies, strategies and techniques in their lessons before the implementation of new constructivist curriculum in Turkey and to see how instruction was implemented at different school settings just before the implementation of the new curriculum in Turkey. The researchers used a descriptive case study approach in which data collected from 10 teachers via observations. The researchers deliberately chose different field teachers with different school settings. The participants in this study consisted of teachers teaching at different fields such as English, Science, Math, Turkish and Computer. The result of this study showed that the teachers wittingly or unwittingly apply almost all instructional theories concerned methodologies and strategies in their lessons to some extent. The results additionally proved that teachers should be better provided with practical training in these applications.