Setting: Last period of the day on Friday. The class is a math class where students have limited English and math abilities.
Me: (Explaining a word problem about orchards and apples. Drawing tiny trees).
Student: (Sitting right in front of me) That's a lot of mota.
Me: (Sounding savvy) Yeh, that a looooooot of mota.
Class: Bursting in laughter
Me: (Confused) What are you guys laughing about? Mota, that means "work", right?
Class: Laughing harder.
Me: Ohhh...trabajo, I meant to say trabajo. What does mota mean?
Class: Not answering, laughing away.
Student: It means marijuana.
Me: Embarrassed, red in a face, joined them in laughter.
It took me five interrupted years of teaching experience to make a mistake like this one. I need to go learn Spanish like five years ago.