One problem is that the “facts” themselves can be controversial. For example, the Charol Shakshaft study cited above was quoted in bits and pieces by some, but was handicapped by an admitted definitional problem. It was a literature review, rather a study in itself, and so was limited by the literature to a definition which conflated sexual abuse with sexual harrassment. Since I have seen estimates of nearly 35 % for the latter, what one can really do with the results is limited, as apparently Prof. Shakeshaft readily admits. The fact that the study gives complex rather simple results makes it less likely to be the subject of a one or two minute report.
But the real issue may be one of perspective. Frankly, I have heard many news reports of sexual abusers being arrested after acts in area schools, and ususally the school was involved in the arrest and prosecution. So I don’t see an obvious bias in reporting on thios subject based on my own experiance. Are some people more sensative to those which affect their religion, and so they notice those more? In the priest abuse scandals what seemed to especially inflame the public was the role that the higher ups played in concealing the crime, and facillitating further crimes, though the priest’s crime was also considered greater than that of the secular abuser because of the additional levels of trust he invoked. The fact that Church authorities were at the same time insisting that laws for non-catholics should conform to the beliefs of the authorities did not help. All of those things make for a bigger story than one about an individual teacher being arrested.
Further, the media sometimes bends to pressure to limit a story, other times responds in reaction to attempts to quash a story. For example, I remember a story that arose from a church spokeperson trying to quash an abuse story by asking a reporter, " How could a good catholic even ask such a question?" The other reporters were not going to leave it alone after that, but I think that spokesman’s attitude is not uncommon among Catholics. And it is presumably why it took so long for many cases of abuse to become public.
The problem of the assignment is to devise a measure of bias that can be used. Since most reported news is of unusual or bad news, a mere count of negative or critical reports is insufficient to show bias.