This dissertation investigated an affective curriculum intervention's effectiveness in resolving underachievement. The intervention was first implemented at a summer program with 20 students and four camp counselors. Inductive analysis of qualitative data indicated that most participants had positive perceptions of the model. Descriptive analyses indicated the intervention had small, positive effects on students' academic self-perceptions (MD = 0.122, SD = 0.621, d = 0.196) and attitudes toward teachers (MD = 0.139, SD = 0.848, d = 0.164) were found. There was no change in attitudes toward school (MD = 0.080, SD = 1.327, d = 0.060) and goal valuation (MD = 0, SD = 0.721, d = 0) and a moderate, negative effect on self-regulation (MD = -0.620, SD = 1.346, d = - 0.460). The intervention was then implemented in a middle school with one 12-year old girl who was gifted and underachieving. An explanatory mixed methods design, combining a single-case A-B design, an interrupted time series simulation, and inductive analysis, was used. The model was perceived as useful, mainly in increasing self-perceptions. Results showed a significant increase in behavioral engagement (d = 1.224, p <.001) and improved achievement (SMD = 1.28). Academic self-perception (MD = 0.57) and attitudes toward school (MD = 1.00) improved, attitudes toward teachers showed no change, and goal valuation (MD = -0.67) and self-regulation (MD = -0.40) decreased. These two studies provide preliminary evidence for the effectiveness of the intervention. [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.]