Many students enter high school with persistent algebraic misconceptions that limit their success in mathematics and, by extension, limit potential educational attainment and future earnings. The purpose of this study was to assess the effectiveness of a warm conceptual change based intervention on remediating algebraic misconceptions held by students at a secondary school. The study used a quasi-experimental, pre-test post-test, control group design as well as student focus groups. In this eight-week classroom intervention, students first took a diagnostic pre-test to identify their misconceptions. For each of seven different misconception categories, students watched a video, took an online practice quiz, and then completed a series of short paper practice slips in class. Students then took a post-test and changes were analyzed. The videos were designed using augmented activation and refutational text to create cognitive conflict. The theorized causal relationship between engagement and conceptual change was explored through analysis of usage statistics, such as the number of times a video was watched. The intervention also explored how interleaved practice and process mnemonics could improve long-term learning retention. A repeated measures ANOVA showed that students in the intervention group made significantly fewer misconception errors than the control group, while regression analysis indicated that deeper engagement led to significantly greater conceptual change. Mann-Whitney U tests showed that the intervention was significantly effective at reducing errors in some misconception categories but not in others. Finally, student focus groups explored how students experienced the intervention. The findings gave strong support for the effectiveness of the intervention at reducing the number of misconception errors students made. [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.bibliotheek.ehb.be/en-US/products/dissertations/individuals.shtml.]