my dad has a great El Paso story...

He was teaching a HS history class...predominantly Hispanic kids. Old, white, retired guy...
He let the banter and craziness go on for the first 2 weeks as if he had no idea what they were saying.
Two weeks up... He responds in fluent slang, not just proper Spanish, to some of the remarks made about him. Class went dead silent.
Little did they know he had been teaching Spanish for over 30yrs, including Spanish to Spanish speakers who needed help, masters degree, etc...
He became their favorite teacher that year.