Becuase right now the school is pretty much writing this off as a simple joke and a matter of freedom of speach. So thereby they should have no problem publishing cartoons that attack other religous symbols. If they do then they show that this isn't a matter of being just a simple cartoon, and shows they do have some kind of Anti Christian biasedness. I mean if it is just a simple cartoon and that is all they meant it to be, then they should have no problem creating the same simple cartoon with another religous symbol.
If not then there could actually be a problem at this school and how they treat religions.