Several questions

I have always said exactly the same thing and so did many others- If this was so good, so profitable why not do it again and again?
Of course I was told of a movie that came out in 1977-78 and no one can remember the name of it as it was a b movie with no name actors in it. I never saw the film myself. But I know the general storyline. It's about a group of semi rich kids attending a prep school. One of the boys is in a car driving with his mother when the mother spots one of his teachers and announces she is going to take the teacher to lunch the boy is angry and begs her not to do so. The mother tells the boy its a good thing to do some degree of brownnosing. The teacher agrees to the moms request, The teacher tells them he knows of a nice diner close by and they drive there. It turns out to be a greasy spoon and the mom has her nose out of joint going there. It has a game room in the back room and the boy gets up and goes into the game room. The mom starts to brown up the teacher and he puts his hand on her knee and starts to move it up her leg. The mother is stunned but doesn't stop him. The boy is playing a video game and a group of lower economic kids about his age come in and watch him play. One of them turns and asks him to give them his prep school blaser. He refuses but eventually gives up his jacket. The mother sees this and gets away from the teacher and rushes into the game room with all the people in the diner watching and demands the kids give the jacket back. The gang switches the table on her and demand she take off her dress and give it to them. This has gotten the attention of all the people in the diner and they are all enjoying watching this. She hems and haws but you see her stepping out of her dress and she stands there in her underwear with all howling laughing at her. The next scene you hear wild laughter and you see the diner from the outside and the door flies open and the mother and her son rush out running. Both are naked and running