David,
You have the right idea, for the wrong reason. HIPAA regulations don't apply here, but FERPA regulations do. And FERPA says that sensitive information should be shared only when there is a "legitimate educational interest". As an instructor, you don't need to know the details of the student's disability -- only that he/she HAS a disability and will need appropriate accommodations as assigned by someone there at the institution.
Dr. Jane Jarrow