Of course, they don't know it yet, but MiB, using criteria beyond the understanding of us common folk, have identified Doyle and Aimee as MiB agent candidates. They've been sent to attend school amongst a variety of alien species and cultures to give them first-hand knowledge of what they'll be dealing with back on earth, and to determine if, indeed, they can deal with it. If not, they'll simply be neuralyzed and have an alternate high school career manufactured for them.