While researchers and practitioners have long known that differentiating formative feedback (FF) is a requisite for creating more equitable learning opportunities for students, less is known about how teachers plan for, enact, and reflect on differentiated FF dialogues with students individually, in small groups, or as a whole class--a lens on practice we refer to as "configurations". This empirical, qualitative case study used a new FF framework to explore how middle-school math and science teachers engaged in FF dialogues with students in different configurations, modalities (written, spoken, nonverbal feedback), and directionalities (teacher-driven, peer-to-peer-driven, self-driven feedback). Findings from analyses of classroom videos, transcripts, and reflections on the use of criterion-referenced assessment tools, including a tool called a "progress guide", found participants engaged in differentiated FF conversations with students more frequently when using scaffolds/tools. Teachers reported more confidence when using progress guides to launch one-on-one and small-group discussions of "first-draft" responses to tasks. The use of progress guides in student-driven self-assessment protocols also increased teachers' sense of self-efficacy in providing differentiated feedback during class time. Results showed that equity-oriented feedback exchanges in high-needs schools centred on visible boundary objects such as progress guides helped teachers and students plan "next steps" with purpose and intention.