Good advice only if one can be sure that the gunman's intention is to kill many children anyway (the flight 93 scenario).

Bad advice if the gunman's aim is to use the children as hostages with something else than killing in mind (the pre 9/11 scenario in most hijackings). If his other aim is threatened by kids throwing things at him he may feel he has to use his gun on the kids contrary to his intitial intentions.

In the worst German school shooting the gunman only intended to kill teachers (killing two kids as well by misfortune). I wonder what he would have done if his former school mates would have acted as recommended. My guess is that he would have killed more kids and less teachers which I would not consider a success.

Wolfgang