In this article, the authors propose a four-part framework for "Critical and Cultural approaches to Ambitious Science Teaching, C[superscript 2]AST," to support educators in grounding learning opportunities in students' cultures and identities and work toward culturally and linguistically sustaining practices. The authors build on previous work with Ambitious Science Teaching, which emphasizes valuing students' ideas and anchoring science units in real-world phenomena (Windschitl, Thompson and Braaten 2018), and offer a critical equity perspective for teachers to consider issues of power, identity, and the sociopolitical context (Gutiérrez 2002). For each principle, the authors begin with a vignette, unpack central ideas, and suggest culturally and linguistically sustaining tips as starting places for science educators.