Four seventh grade life science classes, given curriculum materials based upon Piagetian theories of intellectual development and Skinner's theories of secondary reinforcement, were compared with four control classes from the same school districts. Nine students from each class, who(at the pretest) were at the concrete operations stage of intellectual development, were studied. Both experimental and control groups made significant gains from pre- to posttest on science achievement (Metropolitan Science Test, Advanced Level), but did not differ significantly from each other. The experimental group, however, attained higher levels of intellectual development; the experimental materials facilitated movement from the concrete to formal operations level. Details of the individually-administered Piagetian tasks, the teacher's manual for the experimental materials, one sample of the units supplied to students, and an example of the rating protocol used by the jury validating the materials are appended. (AL)