Here’s an excerpt from They Thought They Were Free: The Germans, 1933-45, an analysis of the causes and destructive path of Fascism before and during WWII. A high school teacher who joined the party to cover for his anti-Nazi past is talking about which Shakespeare plays he could teach:

“Tell me, Herr Hildebrandt, what about Julius Caesar?”

He smiled very, very wryly. “Julius Caesar? No… no.”

“Was it forbidden?”

"Not that I remember. But that is not the way it was. Everything was not regulated specifically, ever. It was not like that at all. Choices were left to the teacher’s discretion, within the ‘German spirit.’ That was all that was necessary; the teacher had only to be discreet. If he himself wondered at all whether anyone would object to a given book, he would be wise not to use it.

This was a much more powerful form of intimidation, you see, than any fixed list of acceptable or unacceptable writings. The way it was done was, from the point of view of the regime, remarkably clever and effective. The teacher had to make the choices and risk the consequences; this made him all the more cautious."