The author will present research on the Slovenian data from the European Collaborative Research Project (ECRP) with some additional national options included. Theoretical background for the research stems from the Dynamic model proposed by Creemers and Kyriakides (2008) and will address teacher factors regarding quality of teaching such as Modeling, Structuring, Application, and Classroom as a learning environment. Teacher factors were evaluated by self reporting questionnaire from teachers and from student questionnaire. Representative sample of Slovenian schools was used (n=59) and within those, results from teachers (n=110) and students (n=2049) of the fourth grade were gathered. This research will explore differences between same teacher factors measured via two different approaches. It will also explore the differential effect on student achievement gain. Results will show the effect of different teacher factors on student’s achievement in Slovenia. The differences between effects from factors measured via different sources of information will give insight into validity and reliability of different ways to measure specific teacher factors.