Book excerpt: We now know much more about the process of language development in all children, and also much more about variations in the process due to multi-cultural and multi-linguistic backgrounds, and developmental anomalies. The book describes both the remarkable changes in language knowledge and use that occur from infancy through high school, and also the differences in the process due to variations in experience. What has been found to be good educational practice during each of these stages is discussed, emphasising that among other things, good practice involves awareness of, and planning for, diversity in the abilities of children.