is it illegal to carry a gun in a school
The Gun-Free School Zones Act (GFSZA) is an act of the U.S. Congress prohibiting any unauthorized individual from knowingly possessing a loaded or unsecured firearm at a place that the individual knows, or has reasonable cause to believe, is a school zone as defined by 18 U.S.C. § 921(a)(25). The law applies to public, private, and parochial elementary schools and high schools, and to non-private property within 1000 feet of them. It provides that the states and their political subdivisions may issue licenses that exempt the licensed individuals from the prohibition.
Gun-Free School Zones Act of 1990