A mixed methods design was used to evaluate the effects of four experiential learning programs on the interest and motivation of middle school students toward mathematics and science. The Expectancy-Value model provided a theoretical framework for the exploration of 336 middle school student participants. Initially, participants were generally positive and had relatively high mathematics and science motivation (Eccles et al., 1983). Overall interest in mathematics increased after completing the program, but a decrease in the importance of mathematics on students' sense of self and some gender differences were detected, with males showing more gains than females. While few significant differences were found on the pre-post student self-ratings, other evidence suggests the program brought about meaningful change. Several potential reasons for the lack of detectable changes on self-reported student motivation measure are discussed. This article concludes with a discussion about the implications for the evaluation of science enrichment programs. (Contains 5 tables.)