This document reports data on 610 secondary level Australian high school students drawn from 36 urban and rural high schools to determine levels of Piagetian cognitive development, provide a profile of field independence (FDI) across the urban population, validate the Understanding in Science Test instrument, and determine influence of reading comprehension and FDI on the validity of group tests. Results for both rural and urban populations indicated a continual growth in cognitive development over the secondary grades with approximately 70% of grade 12 students being measured at the early or complete formal levels. The Understanding in Science Test instrument was not a good predictor of cognitive level of development; reading comprehension and FDI were found to be significant factors influencing the results of group test results. (SL)