This report describes the results of an attempt to identify a learning hierarchy for each of a number of science concepts mainly encountered first in the high school grades. The concepts studied relate to stoichiometric calculations and molarity, both from chemistry; to food web relationships and problems involving Mendel's laws from biology; to problems involving conservation of mechanical energy from physics, and to rock classification problems from geology. A hierarchy validated in terms of its inclusion and transfer characteristics is reported in each case except the last. Further, each hierarchy was examined for the relationship between learner developmental level and acquisition of its component skills. The conformation of the data was not suitable for such examination for two of the hierarchies, namely the conservation of mechanical energy hierarchy and the Mendel's laws hierarchy. For each of the other three hierarchies it was found that formal thought was not necessary to the acquisition of skills which, from a developmental perspective, would have been predicted to be dependent upon it. For each hierarchy data were collected from between 150 and 200 subjects. (Author)