Discussions surrounding assessment in the foreign languages generally focus on the two ends of the teaching/learning process: diagnostic assessment, typically used for placement purposes and administered prior to the start of instruction, and summative assessment, which evaluates learning after instruction for purposes of assigning a grade or determining the efficacy of particular programs or interventions. This paper concerns itself with formative assessment, which takes place during the course of instruction for purposes of enhancing learning. Two overarching points about formative assessment are made here: first, that it is an indispensable pedagogical tool for addressing issues of learner diversity that arise in classes enrolling heritage language learners (HL learners) and, second, that formative assessment is an integral component of the assessment process. In the three-part view of assessment presented here, diagnostic assessment is used prior to the start of instruction to fine tune the curriculum according to the needs of particular classes and to mitigate the challenges of diversity through placement. Formative assessment is used throughout instruction to enhance learning and prepare students with different needs and levels of expertise for summative assessment. (Contains 6 notes and 2 tables.)