NCTM's Principles and Standards for School Mathematics, including documents for pre k-grade 2 and grades 3-5. NCTM also has a section on classroom resources.
NCTE's Standards for the English Language Arts are detailed on this page. The Resources section of their website also includes lesson plans, scholarly research, and groups specific to elementary grades.
A valuable source for research-based professional development video resources, Education in Video contains streaming videos developed specifically for training and developing teachers, .
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A source shining a spotlight on what works in education. We show people how they can adopt or adapt best practices, and we tell stories of innovation and continuous learning in the real world.