This dissertation presents findings from a study investigating of the effects of a middle-school intervention, using the "Skill-Builders" curriculum, on participating students' attitudes, self-efficacy, achievement, self-regulated learning, and classroom learning behaviors in mathematics. The main research questions were 1) will a nine week school-counselor-led intervention using the "Skill-Builders" curriculum have a significant effect on the outcome variables of interest, and 2) will the effects be different for females than for males. A repeated measures ANOVA was used to test for differences between conditions and between sexes on all outcome measures. Results from the study demonstrated statistically significant post-intervention differences between students in the experimental and control conditions on their attitudes toward math learning, self-efficacy, achievement, and self-regulated learning behaviors, and the gains made by students in the experimental condition were maintained at follow-up. Students in the control condition showed no changes or declined on measures of attitudes, achievement, self-efficacy, and self-regulated learning behaviors at post-test and follow-up. Results also indicated a significant interaction for sex and condition, which suggests that the intervention had different effects for the participating females than the males. Implications of the findings, within the theoretical framework of the study and within the context of school counseling outcome research, are discussed.