Mr. Strickland: Am I to understand you're still hanging around with Dr. Emmett Brown, McFly?
[clicks with his mouth, gives Jennifer a tardy slip]
Mr. Strickland: Tardy slip for you, Miss Parker.
[gives Marty one, too]
Mr. Strickland: And one for you, McFly. I believe that makes four in a row. Now let me give you a nickel's worth of free advice, young man. This so-called Dr. Brown is dangerous. He's a real nutcase. You hang around with him, you're gonna end up in big trouble.
Marty McFly: [sarcastically] Ooh. Yes, sir.
Mr. Strickland: [pushes Marty a little bit] You got a real attitude problem, McFly. You're a slacker. You remind me of your father when he went here. He was a slacker, too.