The problems under investigation included (a) Did a directed study of mathematics vocabulary significantly affect student performance levels on standardized mathematical questions? and (b) Did the strategies used in this study significantly affect student performance levels on standardized mathematical questions? The population consisted of eighth-grade pre-algebra students from two different middle schools in southern Indiana. This quasi-experimental study was of a quantitative, repeated-measures design, using a population of approximately 140 eighth-grade students with a control sample of 37 and an experimental sample of 52. I performed a repeated measures ANCOVA to analyze scores from a mathematics vocabulary posttest for each participant, by the treatment and control groups, while controlling for student pretests scores. Results showed that after adjusting for pretest scores (F = 20.12, p < 0.0001), students who received intervention through a directed study of mathematical vocabulary had significantly higher posttest scores compared to the group who did not receive treatment. Students in the treatment group were required to keep a vocabulary journal, part of which was a self-rating of their understanding of each term. At the conclusion of the study, I assigned journal/understanding ratings for each term in the participants' journals. To decide if the journal/understanding scores were associated with pretest and posttest scores, I performed a Pearson's correlation analysis using the continuous variables of journal/understanding score and pretest and posttest scores. There was no significant correlation to the pretest scores for either the student self-rating journal/understanding scores (r = -0.04, p = 0.756) nor the journal/understanding scores that I assigned (r = -0.04, p = 0.756). The results of the correlation analysis showed that the rating of students on their own journal/understanding (r = 0.23, p = 0.103) did not have any correlation with the posttest scores; however, the rating given by the teacher on the journal/understanding of the student was positively correlated with the posttest scores (r = 0.38, p = 0.005). Higher posttest scores were associated with higher journal/understanding scores, with a moderately positive correlation. School professionals such as teachers, administrators, and curriculum directors can assess and review the intervention done in this study and explore replicating or incorporating the approach in their curriculum. With the increase in test scores due to a directed study of mathematical vocabulary, school officials may consider this approach to increase the learning of students and as a result, increase their test scores on high-stakes examinations. [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://www.proquest.com/en-US/products/dissertations/individuals.shtml.]