Naked in School
On ASSTR and elsewhere on the web, there are great stories in the "Naked in School" theme. Originally started by an author named Karen Wagner, it has since expanded into its own genre of erotica, with several interpretations and storylines.
The basic premise is, there is some new government program (often called "the Program"), where a pair of high students are chosen to be naked for a week. They undress at school, and may not wear any clothes until the week is done. While they are naked, teachers may use them as live models, and anybody may make "reasonable requests", such as asking to grope them. They must use the opposite gender's changing rooms and bathrooms during the weak. At the beginning of class, naked students (or sometimes just the boys) may request "relief", where they either masturbate to orgasm, or they have a student "assist" them. I'm sure you can imagine that many sexual hijinks ensue. See here for more information on the format.
There are several variants, such as sex ed programs for middle schoolers, nudity courses in university, etc. This is a hub for stories such as these. You don't have to follow the rules above exactly, feel free to change up what you need. Just make sure it's related to the concepts of nudity, public sex, and school requirements.
The Family Program: