As I'm sure you already know, this is a SIGNIFICANT issue that could have both criminal and educational implications. The short response, is "YES!" a school can discipline a student (possibly both students) for engaging in this type of interaction. Meaning, if the girl did as requested, she could be in trouble, too, at school. Another aspect to consider is possible criminal actions, depending on the specific facts of the case, ages of the students, etc.
I think that you need to consult an attorney who focuses on education law ASAP. You may also need to consult an attorney who focuses on criminal (juvenile) law. It's unclear from your query if you are a parent of either student. In any event, I recommend consulting legal counsel immediately.
Note: I am not licensed to practice law in your state. I simploy provide this response for general, information purposes only. This is not to be construed as legal advice and does not establish an attorney-client relationship. Consult appropriate legal counsel in your area.