Well according to the laws, carrying in a school is against the law. And if you go to school and someone shoots it up, the school should be liable, negligent homicide...
If a school (or other) wants to have a gun free zone then there should be a law requirng them to make sure it remains gun free and offer adequate protection to those who enter. If the school (or other) doesn't want to take on that responsibility then the gun free zone ceases to exist and the existing state laws concerning CC would be in effect.