The objective of this paper is to find out reasons behind low level of reading literacy of primary school students. Since reading literacy is a skill needed for a plenty of learning activities and has to due with students' success in such main areas as language and sciences, authors have studied problem related to students with low reading achievements. If one has a low lever of reading literacy problems in acquiring education might be expected. Data from IEA (International Association for the Evaluation of Educational Achievement) Progress in International Reading Literacy Study (PIRLS) 2001 and PIRLS 2006 are analyzed. The Latvian data about 4th grade students of academic years 2000/2001 and 2005/2006 are used. For each of PIRLS cycles all the students were ranked by their achievement and two subgroups were formed: high-performing group made of top 10% (group A) and low-performing group made of bottom 10% (group B). In the process of secondary analyses of PIRLS 2001 and PIRLS 2006 data factors making the biggest achievement differences between group A and group Z students were searched for. The factors found were grouped in several domains: socioeconomic factors of family, cooperation between student and family members, reading outside the school and reading at school. Factors significance is calculated with regression analyze. Main conclusions are drawn that the socioeconomic situation of the family has a great impact on students reading literacy as well as parent's education and reading aloud to a child in the age of preschool. Students high achieving in reading literacy usually like reading for their own enjoyment and come from families where parents spend a lot of time for reading. Also is find some factors that traditionally count important but really are not significant. As well as the gap between male and female student reading achievements favoring girls was approved. In national context the fact about lower reading literacy level in rural schools was stated. ReferencesElley, W.B. (1994). The IEA study of reading literacy: Achievement and instruction in thirty-two school systems. Pergamon Press, Oxford, UK, 278 pp. Gonzalez, E.J., & Kennedy, A.M. (2003). PIRLS 2001 User Guide for the International Database, Chestnut Hill, MA: Boston College, 240 pp. Linnakylä, P, Malin, A., Taube, K. (2004) Factors behind Low Reading Literacy Achievement. Scandinavian Journal of Educational Research, 48(3), pp 231-249. Martin, M.O., Mullis, I.V.S., & Kennedy, A.M. (Eds.) (2003). PIRLS 2001 Technical Report, Chestnut Hill, MA: Boston College, 266 pp. Mullis, I.V.S., Martin, M.O., Gonzalez, E.J., & Kennedy, A.M. (2003). PIRLS 2001 International Report: IEA's Study of Reading Literacy Achievement in Primary Schools, Chestnut Hill, MA: Boston College, 386 pp.