This book reports valuable research from across the world that addresses questions on what background and contextual factors are related to achievement in mathematics and sciences. All studies utilized data from the Third International Mathematics and Science Study (TIMSS) conducted under the auspices of the International Association for the Evaluation of Educational Achievement (IEA) in 1995, and repeated in 1998. In many countries researchers have started secondary analysis of the data in search for relationships between contextual factors and achievement. In these analyses two different approaches can be distinguished, which can be characterized by the metaphors of 'fishing' and 'hunting'. In the 'fishing' approach, researchers in principle begin with an open mind, considering all possible context variables as possible explanatory variables. Applying analysis techniques like regression analysis, Lisrel, PLS, HLM, and MLn, they try to identify which factors within their countries or across a number of countries. In the 'hunting' approach, researchers have reasons to choose certain context variables upfront and research whether these variables account for part of the variance in the mathematics and/or science achievement. Truely international in scope the book includes contributions from over 15 countries around the world including the USA, South Africa, The Netherlands, Germany and Japan.