Hi, ColoradoTech - Welcome to the forums!
The Wikipedia entry has cites of the law, as well as the text, and copies of the BATF letters which wrongly (in my opinion) make claims contrary to the law.
The crux of the issue is:
The Gun Free School Zones Act states:
(A) It shall be unlawful for any individual knowingly to possess a firearm that has moved in or that otherwise affects interstate or foreign commerce at a place that the individual knows, or has reasonable cause to believe, is a school zone.
(B) Subparagraph (A) does not apply to the possession of a firearmó
(i) on private property not part of school grounds;
(ii) if the individual possessing the firearm is licensed to do so by the State in which the school zone is located or a political subdivision of the State, and the law of the State or political subdivision requires that, before an individual obtains such a license, the law enforcement authorities of the State or political subdivision verify that the individual is qualified under law to receive the license;