Coteach.ai is an AI-powered platform that helps extend and scaffold standard middle-school math curricula into differentiated, personalized learning experiences. By leveraging customized Large Language Models (LLMs) and the Universal Design for Learning (UDL) framework, Coteach.ai generates and retrieves curriculum-aligned educational scaffolds, such as tailored warmup tasks, additional practice questions, and worked examples. Designed to support evidence-based, adaptive teaching, Coteach.ai offers data-driven suggestions for optimal instructional adaptations while compiling valuable insights on how teachers customize their curricula.