Research into the effective teaching of science to emergent bilinguals has converged around key theoretical perspectives and led to expansive empirical evidence that emphasizes the integration of science learning with language/literacy development. Simultaneously, formative assessment has been touted as one of the key components of effective teaching in science classrooms. I address a critical research gap by connecting the teaching of emergent bilinguals in science classrooms to formative assessment through sociocultural perspectives and linguistically responsive teaching--thereby reframing the traditional model of formative assessment into a framework for linguistically responsive assessing. To illustrate the challenges and opportunities of translating a framework of linguistically responsive assessing into practice, I analyzed the formative assessment practices of two middle school science teachers with whom I worked through ongoing professional learning in support of emergent bilinguals through assessing. Both teachers: (1) framed learning goals and assessment around meaningful and relevant student contexts; (2) planned multimodal assessment interactions to scaffold science learning and language/literacy development; and (3) attempted to elicit students' lived experiences. Yet, I also observed missed opportunities that provide additional insight into the continued challenges of ensuring that formative assessment for emergent bilinguals puts literacy and the students' linguistic, cultural, and home/family assets front and center.