school problems with 12th grade

I covered the third conditional once with my 12th graders.

Then the second time.

Then, I held two prep lessons and used 12 sentences as examples.

Every single time someone of them was expected to do something, they'd just stare at the board and ask me what they are expected to do.

Then I gave a test to my pupils.

And got empty tests back.

Then they accused me of maltreating them for expecting them to actually do some work so as to receive the high grades they had before I became their teacher.

Then they asked for some more explanations and prep lessons.

I gave them those too.

Only, nobody was paying attention. I was talking to the walls, and writing on the board for just nobody.

How am I supposed to feel now and what am I to do with them?

(and, yes, the image you see is a photograph of a test I got from an 18-year-old pupil who has been learning English for the past 13 years)