It's a crappy bit of law, with a big loophole.
A loophole that has not been tested in court as being defensible. If a police officer stops you in a school zone, and he KNOWS its a school zone, you can bet you will be arrested.
Is it worth the risk? Each person has to decide that for himself, BUT if your arrested and convicted, its a felony and all the dressings that go with it.
Its irresponsible to tell a person to go ahead and ignore the law without telling them the consequences they face.