How many languages can a person reasonably learn? And not a scholar, an ordinary person. I have a story in which characters are trained from a young age. Part of their training includes language aquisition. Because they are young, I assume that picking up languages would be easy at first. But is it unreasonable or unrealistic to suggest that a group of specially trained individuals could pick up multiple languages as well as other skills before the age of... say... late teens? Thanks.
EDIT: Thanks everyone! You've helped tremendously. I didn't want to say this in my original post, but I currently have one of my charactes at 5 languages. It seems like this is entirely reasonable given what you've all said. And thanks for all the side notes too. I will keep things like switching between languages mid-sentence in mind.