A second or foreign language teacher, unless he’s a native speaker, must learn the language too, together with his students.
Also he must learn many words, to be able to communicate with his students in that language, for instance. And he will learn words if he sees them in a context; otherwise he will not gain those words, if they aren’t in a context.
Because of that it would be perfect if that teacher would read for example a fiction book in that language, English in my case. Thus learning words directly from a dictionary seems that it’s not appropriate nor sufficient. It's my experience, at least.
As well the students will be able to gain more vocabulary if they see those new words also in a context, for example in a simplified and abridged reader or short book.
When learning words is a habit then if you read a novel, you also acquire words: they get stuck in your mind inadvertently and when writing for example they come to mind unexpectedly! It is my own experience. You are creating a vocabulary tank, from which you can retrieve necessary words for communication, which is the goal of that school subject of a second or foreign language. / Photo from: mailman Boston Herald. Those nice workers make communication effective among people.