The accuracy of predictions of future student performance on the basis of graphing data on semi-logarithmic charts and equal interval graphs was examined. All 83 low-achieving students in grades 3 to 6 read randomly-selected lists of words from the Harris-Jacobson Word List for 1 minute. The number of words read correctly and words read incorrectly were scored. Story starters were used to obtain weekly 3-minute writing samples from the 83 students. The compositions were scored for total words written, words written correctly and incorrectly, and correct letter sequences written. Predictions made for the students on the basis of the reading and written expression data collected over 7 weeks were compared to actual data collected for weeks 8, 9, and 10. Analyses of deviations between predictions and actual scores indicated that predictions were more accurate when the data had been graphed on equal interval graphs. (Author/PN)