If he wants to be a history teacher then I really hope he gets that chance and his aspergus doesn't hinder his chances, kids being in contact with someone who has a certain disorder or syndrome (apologies if that's not the right description) and overcoming it, may be a better life lesson than any history lesson.
It shouldn't hinder him in terms of getting a job. My only concern would be how his Asperger manifests itself and how he controls it as schools are stressful places and education is a minefield. I've got several pupils with Aspergers and ea h one is different in their own way, but I love teaching them. I've made a real break through with one and his ability to understand sarcasm and not taken too many things literally.