The 38-year-old, who is currently dating Alex Rodriguez, said that her Bad Teacher co-star is not a "nerd" because he is able to make fun of himself.
Diaz told BBC Radio 1: "He's great at making fun of himself, but if you're really a true nerd, you can't really make fun of yourself that way, you have to be aware of it. He's a bad boy."
The Charlie's Angels actress, who plays a foul mouthed teacher called Elizabeth Halsey in the new comedy, admitted that she lacked interest in academic study at school and would much prefer to give life lessons in dating if she were to teach.
"I was terrible at school, I wasn't interested... Art and P.E. were my favourite. After that I was like, 'What do I need algebra for?'" she added.
"In school there's a lot of things that you spend a lot of time learning that you never actually use in life... So I would like to teach something that's more practical in the real world.
"Dating... Why not? How to have relationships, it's very difficult!"
Watch the trailer for Bad Teacher below (warning: explicit content):