Stanford University proposes to develop and evaluate a proof-of-concept online middle school course (with a teacher version as well) that adapts concepts from the Exploring Computer Science (ECS) curriculum, specifically algorithmic thinking and introductory programming. The project will: (1) Design and deploy an online six-week "Foundations for Advancing Computational Thinking" (FACT) curriculum on Stanford University's instance of the open edX online platform. Aimed at 12 to 15 year-old learners, the curriculum borrows from the ECS Programming and Problem Solving units. It will be driven by short video lessons with in-video and stand-alone quizzes for formative and summative assessments, and programming activities. (2) Pilot FACT in a Bay Area public middle school class. (3) Empirically examine the efficacy of: (a) the curriculum for the development of computational competencies, preparation for future learning of computing, and changes in student perceptions of CS via assessments designed for these purposes, and (b) student attitudes towards and experiences with online learning, including online course features such as in-video quizzes and discussion forums. (4) Create and pilot an appropriately enhanced version of the curriculum for teachers to effectively prepare them to facilitate FACT/ECS use in their classrooms.