This toolkit provides activities and resources to assist practitioners in designing and delivering intensive interventions in reading and mathematics for K-12 students with significant learning difficulties and disabilities. Grounded in research, this toolkit is based on the Center on Instruction's "Intensive Interventions for Students Struggling in Reading and Mathematics: A Practice Guide." The practice guide examines four considerations for intensifying interventions: (1) supporting cognitive processes; (2) differentiating and intensifying instructional delivery; (3) increasing instructional time, and (4) reducing group size. Although progress monitoring of student learning is a critical step when implementing intensive interventions, this topic is outside the scope of the practice guide and, therefore, is not included in this toolkit. (Contains 1 figure.) [For related report, "Capacity Building Indicators & Dissemination Strategies: Designing and Delivering Intensive Interventions--A Teacher's Toolkit," see ED536128.]