In general, it shall be unlawful for any individual knowingly to possess a firearm at a place that the individual knows, or has reasonable cause to believe, is a school zone. This does not include possession of a firearm on private property that is not part of school grounds.
The term school zone means in, or on the grounds of, a public, parochial or private school; or within a distance of 1,000 feet from the grounds of a public, parochial or private school.
The term school means a school which provides elementary or secondary education, as determined under State law.
Exemptions:
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 obtain 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; which is...
Basically, a state like NY that issues CCW permits, it would be legal to carry a licensed handgun in a school zone, except THEY (NYS) have/has their own law saying NO guns on school ground without permission of the school district.
Apparently Private Colleges are able to make up their own minds (??).
MIGHT be interesting to note the 1st attempt at this federal law was deemed unconstitutional, so they added an "interstate commerce clause" comment to it and had it repassed.
California has their own too: Enclosed are University of California implementing guidelines for the California Gun Free School Zone Act of 1995...
http://www.ucop.edu/ucophome/coordrev/policy/8-16-99gun.html