As I'm sure most of you know, the 1990 "Gun-Free School Zone Act" was ruled unconstitutional in U.S. v. Lopez, however it was amended in 1995 and that version is still on the books as current federal law.
The current law can be found here and here is the pertinent part of the law from the Delaware AG's website.
Under current law you cannot carry in a "school zone" (within 1000ft. of a school) unless you have a CCW permit issued from the state in which the school resides. Open carrying? You'll have to stay out of "school zones" at all times or risk becoming a felon unless you also have that state's CCW permit. Carrying concealed in PA on a Utah CCW? watch out for school zones.
Just how are you supposed to know whether you're within 1000 ft. of a school, especially if carrying in an unfamiliar area? (I.E. out of state) Even in Newark, I'm not 100% sure where the 1000ft. radius around Newark High School extends to. Also, the law contains the phrase,
"that the individual knows, or has reasonable cause to believe, is a school zone"
This means you'd be better off not ever reading the law in question nor acquiring knowledge of where the schools are in the area(s) in which you will be carrying. Ignorance is innocence.
Someone I know may have at times thrown his/her guns in an unlocked range bag to go shooting at Ommelanden and driven right past William Penn High School, thus passing through a prohibited "gun-free school zone."
In light of Heller I think this law could end up being challenged at some point down the line and ruled unconstitutional.