What does 呼ばれてる mean in this context?

Question

I’m reading a story, and in it 2 students are talking about a teacher. One says, ね、榎本先生ってさ。。。 男子にエロ本って呼ばれてるらしいよ。This is followed by a scene where the boys were caught with a prön mag, and the teacher telling them they have to be more careful about it. She later confronts him about it saying, 先生はエロ本って呼ばれてるじゃん。

I have no clue how to interpret this usage of 呼ばれてる as I’m certain it can’t mean “call” as that wouldn’t make sense.

Answer 1

I think this in fact something that the boys have been calling this teacher (presumably behind his back), as a kind of pun on his name, 榎本{えのもと}. (They are deliberately mispronouncing the first character as エロ instead of えの.)

Edited to add: The above answer was premised on the assumption that you understood the grammar but thought 呼ぶ must have some meaning other than "call" because you couldn't understand why the boys would be calling the teacher such an odd thing. Since Chocolate has suggested in a comment that it might be the use of the passive voice that's throwing you off, I'll just add that 呼ばれてる doesn't mean "call," but "is being called."

Answer 2

榎本先生ってさ。。。 男子にエロ本って呼ばれてるらしいよ。

(Though I'm not sure where your confusion comes from...) Let me break it down to smaller parts:

榎本先生って -- "As for Mr. Enomoto... / Mr. Enomoto is..." (≂「榎本先生は」)
^{(The って is the colloquial version of the topic particle は)}
さ -- filler
男子に -- "by boys / by male students"
エロ本って -- "as エロ本" (≂「エロ本と」)
^{(The って is the colloquial version of particle と)}
呼ばれてる -- contracted pronunciation of 呼ばれている.
(呼ばれている is the progressive form of 呼ばれる. 呼ばれる is the passive form of 呼ぶ.)
らしい -- "It seems like... / I hear that..."
よ -- sentence ending particle 　

The basic structure of this sentence is:

XはYにZと呼ばれているらしい。
I hear that X is called Z by Y.
榎本先生は男子にエロ本と呼ばれているらしい。
I hear that Mr. Enomoto is called エロ本 by boys.