The optimal age to start learning a second language is an issue that concerns parents, teachers, researchers, and policy makers. Studies that have evaluated the beginning stages of school language learning have found that teenagers and adults learn languages faster and more accurately than young children. In seeming contrast to this, younger learners consistently outperform older learners by attaining native-like proficiency and phonological competence. This suggests that older learners are initially fast at acquiring the grammar and structure of a language but are eventually surpassed by younger learners on most, if not all, linguistic parameters. Many theories have tried to explain this phenomenon, principally theories which deal with the cognitive differences between ages, the affective-motivational differences between ages, the fact that younger children have more time available to study than older children, and the biologically-based critical period theory. In order to assess whether early language teaching is an effective practice, an experimental project was carried out in five Tel Aviv schools. This monograph reports on the results of this experimental project.