The United States Federal Government regualtes Firearms that have moved in, or otherwise effect, InterState Commerce from being in, on, or within a 1000 feet of any Public Primary or Secondary School. The correct Federal Law governing this instance is 18 U.S.C. 922(q).
Many States have Laws that govern the possesion of Firearms in or on, or in some cases within a 1000 feet of, School Property as well. However, and most often, these Statutes tend to be stricter than Federal Law in several aspects, among them: 1. School Zone Statutes often implemented in the States tend to cover Private Schools, in addition to Public Schools, among the States Prohibitions, 2. Sometimes..., but not always..., these 'School Zones' include Public or Private Colleges or Universities, which; is something Federal Law has no bearing on, 3. Some States, but not all States, include DayCare Centers, PreSchools, and PreKindergartens, 4. In some States the 1000 foot rule is alive and well, but in others is not authorized per Statute, and 5. In some States, having a Firearm on School Grounds or in School Buildings is only a Misdemeanor, but in other States the Crime still remains a Felony.
Eye95 is correct in that Federal Law 18 U.S.C. 922(q)(2)(B)(ii) only exempts Persons who are holders of Valid StateSide Licenses wherein the School is found, only if, and only if, however, the State must first be Brady Act and National Instant Criminal System Act complinat prior to the Licensure of a Private Citizen.
There are currently two States, 1. Illinois and 2. Wisconsin..., that do not issue Licenses at all to Private Citizens for the purpose of Open or Concealed Carry.
Therefore, in the unique Cases of the two aforementioned States, a Person who is in, on, or within a 1000 feet of any School in either Illinois or Wisconsin automatically Violates 18 U.S.C. 922(q), unless; they can prove one of the three remaining exceptions under: 18 U.S.C. 922(q)(2)(B)(i), 18 U.S.C. 922(q)(2)(B)(iii), or 18 U.S.C. 922(q)(2)(B)(iv).
In every other State in our Country, it depends what State Law says. There are currently Eight States, namely among them: 1. Utah, 2. Oregon, 3. Alabama, 4. Rhode Island, 5. Delaware, 6. New Hampshire, 7. Michigan, and 8. California, that specifically Authorize Carry of Firearms by License Holders on all Public School Property. Although most of these States have 'Shall-Issue' Licensure Laws, two of them: 1. Alabama, and 2. California are 'May-Issue' in Nature.
Notice, Federal Law says nothing about Carrying a Firearm to or while at Colleges or Universities, and as a result, are Regulated, to various degrees, by State Law, pending several factors..., namely: State-wide Preemption. However, it is not uncommon for College or University Regent Boards of Public Schools to threaten Administrative or Displinary Sanctions against Students and Faculty, respectfully, who Carry Firearms on College or University Property. Needless to say though..., in the Case of Public Colleges/Universities..., State-wide Preemption prevails over any such rule or Regulation implementation over a Regent Board, or its equilvalent, should they press the issue.
If your State is not listed 1-8, of the listed States above, then, it is highly advisable to review your States Law to see what does, and does not, apply to Firearm Carry at Public School Property, and if so..., to what Degree or Level or Educational Instruction.
In my State, Georgia, Georgia Law 16-11-127.1 Prohibits all Carry on all School Property, regradless Public or Private, regardless the Level of Instruction. There is NO more 1000 foot rule, however; as it was Repealed by The Legislative Acts of The Georgia General Assembly SB 308 2010. MERELY being within a 1000 feet of a School, any School, in Georgia with any Weapon is OK. It is also Legal to have a Weapon in your Vehicle without further Governmental Intrusion into your Private Business for such Vehicles that happen to be Parked on School Property. The term 'School Property' also includes the Board of Eductation Offices of each County and City School System (when a City has one), and also applies to The State Education Board Office in Atlanta. Any Person who can claim an exemption under 16-11-130, regarding Governmental Personnel, are exempt. Furthermore, if, and only if, you have a Georgia Weapons Carry License, it is only a Misdemeanor, BUT in ALL other Cases it is a Felony. The definition of 'Weapon' is also a lot more encompassing than what 'Weapon' is defined under Georgia Official Code Annotated 16-11-125.1. As far as the Level of Protection that Schools recieve..., 'Weapon' could mean anything down to Finger/Toe NailFiles, or a Highly Sharpened #2 Pencil. It is not pratical..., BUT is Possible..., to recieve a 'Weapon on School' Charge for having such objects..., but for all pratical purposes..., it usually does not happen.