The normal human brains ability to pick up linguistics easily is confined to under the age of 8. After that it becomes progressively and progressively harder to pick up foreign language. Waiting until junior high or high school to start teaching foreign language is waiting 10 years later than the natural human ability to pick up language evolved. So the time to teach foreign language is the very earliest possible. Preferably in preschool and kindergarten and elementary school because that is when the human brain is most keyed to absorb linguistic information. Children that are bilingual or poly lingual inevitably were exposed to those languages very young. Either by having a family language that was spoken in the house that was different than the main language spoken outside. Or by having grandparents or a family members or domestic servants that spoke different languages. But intrinsically the human brain evolved to pick up languages young and so that is when we should teach it because that takes advantage of a natural evolutionary process to the benefit of children.