I'm with Lilly on this one... Even if going to BA requires a shift of style or method, it shouldn't ruin the teacher's dancing any more than learning Mambo would ruin someone's Salsa. Make you think about it a little harder because of the similarities vs the differences, yes. But RUIN the first dance? No. The only benefit-of-the-doubt I can offer is if the person meant dancing in BA would "ruin" them for their local scene... as in.. "it's going to be so good there, it will ruin me for coming back to my limited local scene and dancing with the chuckleheads here". Not that a teacher should have that attitude about their local scene either, but it's the only connotation of being "ruined" by BA that makes ANY sense to me!