Visual aids and multimedia contribute positively to the pedagogical value of in-class and eLearning education. In this paper, we experiment with a visualization tool to gauge its effect on the test scores and, by implication, the understanding levels within Data Structures course offered at Junior level for Computer Science students. Data Structures constitutes an important foundation topic in computer science education which many students fail to do well at due to the complexity of some of its concepts and theories. Therefore, we anticipate that this (Java Applet) tool will support the teaching and help students better understand the (C++) coding and algorithms relating to Binary Search Trees (BST). The test pool is a segregated learning environment which enables us to look at the effect of visual aids on gender as well. The percentage of test score improvement between the group of students who use the visualizer and those who do not ranges between 10 and 13 percent. Although, male students do perform slightly better with the help of the visual aids, the difference in performance does not constitute a major advantage that supports gender related performance theories