Once your medical information gets into the hands of the school FERPA does apply. Usually, this medical information is related to educational activities. For example IEP or individualized Education Plans. Also, school nurses who do have your actual medical information are not bound by HIPAA, they are bound by FERPA.
http://www2.ed.gov/policy/gen/guid/fpco/doc/ferpa-hipaa-guidance.pdf
V. Frequently Asked Questions and Answers
1. Does the HIPAA Privacy Rule apply to an elementary or secondary school?
Generally, no. In most cases, the HIPAA Privacy Rule does not apply to an elementary or
secondary school because the school either: (1) is not a HIPAA covered entity or (2) is a HIPAA
covered entity but maintains health information only on students in records that are by definition
“education records” under FERPA and, therefore, is not subject to the HIPAA Privacy Rule.
quote from above website
My point Chamonix is that your medical record "become" educational records when the information is obtained by the school system. Thus HIPAA no longer applies.