Grit, defined as “perseverance and passion for long-term goals,” is considered an important noncognitive factor for promoting academic achievement and closing the racial achievement gap. School-based policy and intervention work, however, is getting ahead of the grit research. Specifically, it is unclear to what extent grit overlaps with existing noncognitive variables as a construct and measure. It is also unclear whether grit predicts later achievement when accounting for other noncognitive variables, and if grit and other noncognitive variables predict achievement differently for students from different demographic backgrounds. Using exploratory and confirmatory factor analysis within a self-regulation framework, I evaluated grit’s conceptual and operational overlap with similar noncognitive factors of engagement, emotion regulation, and growth mindset in an ethnically diverse 3rd, 4th, and 5th grade student sample (N = 192). Using structural equation modeling, I tested if grit predicted literacy achievement 1-3 months later, in a model also adjusting for similar noncognitive factors and for previous (Time 1) literacy achievement. Finally, I compared the predictive model by age, ethnic group, and bilingual status to determine which noncognitive factors predicted literacy outcomes for which groups of students. Results indicated that, among diverse elementary school students, grit and other noncognitive constructs are not lower-order factors of an overarching self-regulation construct. Grit was moderately related to, yet distinct from, growth mindset and emotion regulation, while it overlapped excessively with engagement. Grit and engagement as a joint construct did predict later literacy achievement, but not after controlling for previous literacy achievement. Relations among grit, engagement, and literacy achievement were different for ethnic and linguistic groups, but again these differences were eliminated after controlling for previous literacy achievement. Research lacks compelling evidence that grit, at least as it is currently measured, is a relevant predictor of diverse students’ short-term literacy outcomes. Researchers and educators are thus cautioned against focusing on grit as an assessment or academic intervention tool for improving ethnic minority or bilingual students’ reading; a focus on previous achievement and building literacy skills continues to be best practice for promoting future literacy achievement.