The purpose of this study is to examine the effects of some of the changes such as student centered learning (i.e. inquiry science instruction), outfitting classrooms with latest technology and computers that the reform movement has brought about on students' TIMSS 2007 science achievements. Two-staged stratified sampling was used in the selection process, in which schools and classes were sampled in the first and second stage, respectively. TIMSS 2007 study were administered to students, teachers and principles in 145 classes in 145 schools. On average, 28 students from each school participated in the study. The results of the hierarchical linear modeling (HLM) analyses indicate that while computer access positively influence students' science achievements, inquiry science instruction negatively influences students' science achievements. Furthermore, it has been found that students' science achievements increase in parallel to an increase in the socio-economic status (SES) of the families, teacher experience and students' self-confidence in learning science. Finally, the effects of inquiry science instruction, self confidence in learning science and gender on TIMSS science achievement have been found to significantly vary among schools.