This qualitative single case study explored how general education middle school teachers implement the three tiers of the Multi-Tiered Response to Intervention (MTSS/RTI) model while delivering differentiated core curriculum instruction. The conceptual framework included the differentiated strategies of Fleming and Mills' (1992) Visual, Aural, Read/Write, Kinesthetic (VARK) model; Vygotsky's (1978) concept of Zone of Proximal Development (ZPD); and Wood, Bruner, and Ross' (1976) concept of scaffolding. The sample group consisted of 11 general education middle school teachers in a single Central Florida school district. The data sources included an online questionnaire, interviews, and one focus group session. The macro-level research question that guided this study was: "How do general education middle school teachers implement tier one, tier two, and tier three of the MTSS/RTI model while delivering differentiated core curriculum instruction?" The analyzed data produced four themes: (1) tiered intervention strategies, (2) tiered progress monitoring measurements and frequency, (3) tiered documentation of responsiveness to interventions, and (4) tiered delivery of differentiated core curriculum instruction. The findings provide insightful perspective to general education middle school teachers, leading to an increase in the successful implementation of the three tiers of the MTSS/RTI model. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://www.proquest.com/en-US/products/dissertations/individuals.shtml.]