Studying ethics is not about "this is right or wrong", it's about "these are ways to consider what is right or wrong". It's one level higher in terms of "metaness" than you think it is.

If an ethics course teaches students which decisions actually have an ethical component in them, that's already a huge win: Whenever they encounter such a decision, they will be more likely to notice and ponder the ethical implications contained therein. This does not necessarily prescribe a particular set of ethical rules that they have to adhere to.