The original Sheltered Instruction Observation Protocol (SIOP) Model was developed by researchers Jana Echevarria, Mary Ellen Vogt and Deborah J. Short under the auspices of the CAL and Center for Research on Education, Diversity & Excellence (CREDE), a national research center funded by the U.S. Department of Education.

The SIOP Model is a research-based and validated instructional model that has proven effective in addressing the academic needs of Multilingual learners, However, through extensive work with schools, districts, state education agencies, and organizations, CAL has expanded and enriched the model to include more than just the eight components and their respective features.