Abstract
Online learning is one of the fastest growing trends in Technology- Enhanced Learning (TEL). Technology in combination with an instruction that addresses the cognitive and social processes of knowledge construction could offer more diverse and effective online learning opportunities than their face-to-face counterparts. In this review we attempt to summarize different forms and practices in K-12 online and blended learning as they appear in various regional, national and cultural contexts. The article starts with introducing some basic concepts and terminology, sums up the state of K-12 online learning around the world and ends with summarizing some trends and challenges observed in current K-12 online learning practices.