DE law has the gun-free school zone as a additive charge AFTER a crime is committed. Open carry is lawful, so you can Open Carry in a school zone.
I OC within 1000 ft of a school all the time as I live that close to a school. I've waited for my kids to cross the street from school when I walked them home.
Going onto school property (not into a building) is also technically allowed, but I haven't tried it.
“I prefer peace. But if trouble must come, let it come in my time, so that my children can live in peace.” -Thomas Paine