Writing, speaking and listening are communication skills that are important in all subject areas in the curriculum. Hence, literacy should have a central position in the curriculum. Even so, differences between students' levels of literacy mean that some students fail to acquire the verbal foundations for learning. For this reason, increasing numbers of students fall short of proficiency as they proceed through the school. This booklet, the fourteenth in the series on educational practices that generally improve learning, responds to calls for principles and teaching practices that address the worldwide problem in increasing literacy skills. It draws on educational research and extensive experience with classroom practices to explain important principles for increasing literacy. In contrast to reading, less definitive scientific research is available on the other three language skills discussed in this booklet. For this reason, the limited research is supplemented here with the insights of experts and educators with long and varied experience in the teaching of language skills. The officers of the International Academy of Education are aware that this booklet is based on research carried out primarily in economically advanced countries. The booklet, however, focuses on aspects of language skills that appear universal.