This study examined the ability of junior high school students to use advance information when making semantic category decisions. The subjects, eight good readers and eight poor readers, identified paired words as "same" or "different" in category, with some words more highly associated with the category than others--in the "fruit" category, for example, "apple" is higher in value than "kumquat." Advance information (the name of the category) was presented either aurally or visually in half the trials. A comparison of subjects' reaction times with the reaction times of a college-student control group indicated that junior high school students are still developing their semantic memory networks and that good readers are apparently farther along in this development: the good readers in the study benefited from advance information, especially in the auditory mode, whereas the poor readers showed less semantic ability, even with the highly identifiable words, and did not benefit from advance information. The study concludes that this evidence may indicate why poor readers experience greater difficulty with the more complex semantic tasks of reading. (RL)