One theoretical extension of Optimal Distinctiveness Theory (ODT; Brewer, 1991; Leonardelli, Pickett, & Brewer, 2010) is that individuals will work toward the satisfaction of their own social identity needs for differentiation (standing out) and assimilation (fitting in). Because these needs serve as driving forces behind the attitudes people adopt, and the behaviors they enact, the motivational properties of these needs are likely to be manifest in achievement contexts. Bridging ODT and Expectancy-Value Theory, this article examines the prediction that academic tasks are seen by students as more important when they contribute to students’ ability to stand out (task differentiation) from and fit in (task assimilation) with their classmates. This prediction was supported among an ethnically diverse sample of STEM-focused high school students who rated the importance of 18 mathematics-related academic tasks. Additional analyses demonstrated that the association between task assimilation and task importance was stronger for students who perceived their academic learning environment to be performance-focused (performance goal structure). There also was a significant interaction between task differentiation and task assimilation, such that the association between task assimilation and task importance attenuated at higher levels of task differentiation. The present study is one of the few investigations to assess how students’ valuing within a single academic domain might fluctuate from one academic task to the next (e.g., taking notes versus working out problems on the board). The Discussion addresses the theoretical and practical significance of acknowledging differentiation and assimilation as vehicles for motivating students in the classroom.