Biology, Chemistry, Earth Science, Physics, and Ecology assessment instruments were administered to approximately 1,800 nine year old and 1,800 seventeen year old Massachusetts students. The 9 year old students exceeded the performance of a national and international sampling of students. They equaled the performance of a sampling of students from the northeastern United States. Seventeen year old students equaled the performance of the national sample, but fell below the achievement of both the northeastern and international samples. Both 9 and 17 year old students from residential suburban and other communities tended to perform higher than those students from the large city and industrial suburban communities. For both 9 and 17 year olds, about twenty background and experience factors were examined for their relationship with assessment performance. Most of the association between these factors and achievement in 17 year olds was accounted for by the amount of laboratory experience that the student had in physics and chemistry, and whether or not the student reported discussing scientific matters with friends outside of school. The three factors that appeared most often for 9 year olds were type of community, parents' occupation, and sex. (Author/CTM)