Middle school is one of the most important times during which students gain knowledge. However, a large proportion of adolescents have continued to complete middle school without mastering essential knowledge of, and skills in, vocabulary and reading comprehension. Adolescents who miss school in the 30-60 days leading up to high-stakes exams experience declines in their reading scores. The aim of this study was to examine the effects of selected demographic factors on the reading achievement scores and attendance of middle school students. Specifically, this study involved examination of the effects of socioeconomic status (SES), gender, and ethnicity--both separately and in combination--on the vocabulary scores, reading comprehension scores, and total reading scores of middle school students in the reading section of the State of Texas Assessment of Academic Readiness examination. The study also involved investigation of the effects of SES, gender, and ethnicity--both separately and in combination--on the attendance of middle school students. A 2 x 2 x 4 factorial research design was used in this investigation, and 480 middle school students were randomly selected to participate. Both student-level attendance records and standardized reading scores were analyzed using three-way analysis of variance. This study results confirmed that SES, gender, and ethnicity were driving factors behind differences in the reading achievement scores and attendance of middle school students. Results indicated statistically significance differences in vocabulary scores, reading comprehension scores, total reading scores, and attendance of middle school students based on SES, gender, and ethnicity, both separately and combined. The results suggest that other factors are likely involved in differences in the reading scores of middle school students. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://bibliotheek.ehb.be:2222/en-US/products/dissertations/individuals.shtml.]