This document outlines 10 lessons learned from 10 years of research on K-12 online teaching and learning. The research has been exploratory in nature using surveys, case studies, and qualitative methods. Few experimental designs have been used. Early research focused on comparing online to face-to-face, but questions have shifted to understanding online learning itself. Successful online teachers are experienced, lifelong learners who play multiple roles, but need tailored training. Successful online students are motivated, organized, independent learners from environments conducive to online learning. Much more research is still needed, especially comparative and data-driven studies, to fully understand online teaching and learning.