My previous post suggested that police in West Virginia respond differently to misdeeds of students than to misdeeds of teachers. It occurred to me after writing it that I had seen a similar pattern in a very different society, and the two may have the same explanation.
One of the features we associate with oppressive regimes is forcing children to testify against their parents. Imperial China, which is the subject of one chapter in my current book project, did the precise opposite. For a child to accuse his parent of a crime was a criminal offense, whether or not the parent was guilty.
My explanation of that (and some other features of Chinese law) was that the government was ruling a very large population with a very small number of elite scholar-bureaucrats. It did it by subcontracting much of the job of controlling behavior to other authority structures, of which the most important was the extended family. A child who could threaten to report a parent's crimes to the state would have leverage over the parent, undermining the hierarchical authority structure of the family. Preserving that structure was important enough so that the state was willing to give up a little of its ability to enforce its own laws in order to do so.
I suspect that, in a modern society such as ours, much the same pattern holds for the relation between the authority structure of the police and the authority structure of the school. The police expect the school to take on a good deal of the job of controlling students. A policy of backing teachers against students when the two come into conflict helps support the school's authority structure, however badly it fits with an ideology of equal rights for all.