I remember seeing this movie about 20 years ago on VHS. I’m pretty sure it was made in the 80’s and would be considered a Teen Sex Comedy. It was English and in color.
Near the beginning of the film, the reserved parents of a wild girl decide to send her away to a new school to receive a proper education.
Most of the movie itself is a blur, but the ending is clearer in my memory: There is a meeting at the school and the girl’s parents are there as well. There is a plot in the movie concerning a photo taken of another student having sex. The photo is enlarged and put on an easel and shown to the crowd. Behind the photo is a small explosive device. As the frustrated parents go to leave, the bomb explodes. The smoke clears to show the mother wearing black lingerie and the father wearing heart boxers and a t-shirt with “Hot Stuff” or something written on it. The father than says “Now… this is not what it appears to be!” and the mother says “Oh, forget it, (name)! They got us.” They make up with their daughter and all is well.
This has been driving me crazy since I can clearly remember this scene but can’t find any movie that has it.