Well, I'm almost there, but not quite.
Red Cross cites "Third Geneva Convention (with respect to prisoners of war), the Fourth Geneva Convention (with respect to protected civilians) and Additional Protocol I (with respect to civilians in general)" as the source of the legal definition of "human shields."
They also summarize the following:
Definition of human shields
The prohibition of using human shields in the Geneva Conventions, Additional Protocol I and the Statute of the International Criminal Court are couched in terms of using the presence (or movements) of civilians or other protected persons to render certain points or areas (or military forces) immune from military operations. Most examples given in military manuals, or which have been the object of condemnations, have been cases where persons were actually taken to military objectives in order to shield those objectives from attacks. The military manuals of New Zealand and the United Kingdom give as examples the placing of persons in or next to ammunition trains. There were many condemnations of the threat by Iraq to round up and place prisoners of war and civilians in strategic sites and around military defence points. Other condemnations on the basis of this prohibition related to rounding up civilians and putting them in front of military units in the conflicts in the former Yugoslavia and Liberia.
In the Review of the Indictments in the Karadžić and Mladić case, the International Criminal Tribunal for the former Yugoslavia qualified physically securing or otherwise holding peacekeeping forces against their will at potential NATO air targets, including ammunition bunkers, a radar site and a communications centre, as using “human shields”.
It can be concluded that the use of human shields requires an intentional co-location of military objectives and civilians or persons hors de combat with the specific intent of trying to prevent the targeting of those military objectives.
I'm getting tired, so I may be getting sloppy, but I don't see how hiding rockets in a vacant school is "using the presence (or movements) of civilians or other protected persons to render certain points or areas (or military forces) immune from military operations." I mean, how are you rendering a point immune from military operations if you're hiding rockets there?
I don't know. Maybe I'm descending into sophistry, but I have a cynical suspicion that international law is all about sophistry.