The teacher at P.S.129 in New York City was teaching her third grade class  about farm animals. 

She asks the Italian kid, "Mario, what does a chicken sound like?" 
Mario replies, The chicken, he go cluck, cluck, cluck." 

"That's correct," the teacher says.  To an Irish kid, she asks, "Patrick, what  does a cow sound like?" 
Patrick answers, "The cow goes mooo." 

"Correct," responds the teacher.  To the black kid, she asks, "Tyrone, what does a pig sound like?" 

Tyrone shouts, "Freeze, motherfucker!"