I'm actually an English teacher myself. The first thing I teach my students is that all they have to do is show me the meaning they get out of the text, and how they get it. What I think about the text doesn't come into the equation - so long as they can argue their point effectively, there is no reason why they cannot do well. For example, in setting an assessment task on Romeo and Iuliet, I might ask the following question: "Are Romeo and Juliet experiencing genuine romantic love, or are they simply going through a teenage phase? In your answer, consider both sides of the argument, drawing on evidence from the text to support both cases before coming to a definitive conclusion."
So, in answering, they may say that Romeo and Juliet experience genuine romantic love because their deaths are not some grand gesture intended to make a statement to their families, but the end result of a series of unfortuante twists of fate that lead to Romeo never receiving a critical messge. On the other hand, Romeo is compeltely infatuated by another girl, Rosalie, before encountering Juliet; upon meeting her, her falls for Juliet and forgets that Rosalie ever existed. So there's the evidence for both cases, and at the end, the student has to decide which case is stronger (clever students will deliberately pick out weak arguments for the case they do not support). So they've shown both a) the meaning they get from the text, and b) how they get it. Any essay that does that is pretty much guaranteed a high mark.
The point I'm trying to make is that it's not about the difference between what the author meant and the teacher thinks. Any teacher who teaches that way is pretty poor at their job.