This is a collaborative research project between three universities. The project is a comprehensive, systemic research and development program addressing three inter-related tiers of study: student learning and development; teacher beliefs, knowledge, and practice; and professional development. The project is grounded in both sound theory of how students develop algebraic reasoning and acquire domain knowledge and skills and in the beliefs and existing practices of teachers. In the student tier a detailed developmental model of students' evolving algebraic reasoning and skill acquisition will be constructed concentrating on the transition from arithmetic to algebraic reasoning. In the teaching tier a promising pedagogical approach, Bridging Instruction, will be tested. In the professional development tier a teacher professional development prototype will be implemented. The prototypeT extends an existing technology based approach. It enables the evaluation of a scalable model of teacher professional development. Technology is a central aspect of this project. The findings of this research will be implemented into a coherent educational program for students and teachers using Algebra Cognitive Tutors and the STEP web teacher professional development environments.