As online and blended learning gain more popularity in education, it becomes more important to understand their effects on student learning. The purpose of this study was to explore the effects of self-paced blended learning of mathematics on the attitudes and achievement of 26 high ability middle school students, and investigate the relationship between perceived effectiveness of self-paced blended learning and achievement growth. Findings revealed that attitudes toward mathematics and students' value of mathematics improved as a result of the self-paced blended course. Achievement growth during the traditional course the year prior and during the self-paced blended course was not significantly different.