An instructional design based on task analysis procedures was used to develop two experimental lessons to accelerate attainment of a subject-matter concept by fourth grade students. A variation of the Solomon Four-Group design was employed to determine the effects of the pretest. Performance of 118 randomly assigned subjects on a measure assessing two levels of concept mastery showed that experimental groups performed significantly better at both levels than control groups. Effects of the pretest were not significant. A two-month follow-up assessment revealed highly comparable results. (Author)