I think all of us teaching English, have to remind ourselves that though it might seem that our students understand - a lot of the time, even most of the time, they are faking it.
I remember especially in my first years of teaching, fully thinking that the nodding, the "yeah, yeah", "ok" of my students indicated that they'd understood. However, what was happening was probably much like this famous Far Side comic.
Our students often are "bewildered" (to borrow a term Frank Smith uses often in reference to children learning to read). There is overload and the brain is overcome. But there exists a powerful need to believe in the pragmatic elements of communication (the facial expressions, gestures, eye contact etc..), also the hints and inferences of half meaning that pass along as communication. We want to understand so much and we want to communicate and please the other so much - that we "fake it". Nobody wants to say, "I don't understand".
Not that faking it is all bad. It is only bad if "learning" is your aim. If you want to be social, faking it can be a great strategy. Or if you are asking for directions in Spanish and are confronted with a flood of Spanish that you can't understand at all - it can be a quick way out of a sticky situation.
Still, as a teacher, we should be aware of how learners, "fake it". Otherwise, we can't adjust our lessons and content appropriately and we become teachers who "fake it". And yes, they exist! In my experience, "faking it" is an art undertaken in abundance by teachers. Like the Cuban joke about communism, "they pretend to pay us and we pretend to work", --- "teachers pretend to teach and students pretend to learn". It happens a lot.
So be aware of the dynamics of communication in the classroom. Do your students really understand you? (and they don't have to understand everything but they also shouldn't be overwhelmed). If they are faking it, it is time to think through your lesson delivery and maybe do a few of the following;
1. Model more, explain less. Think through how you'll explain the stages and activities of the lesson.
2. Get Ss speaking and doing the explaining. They'll bring it down to the level of the audience and the communication will be much more effective.
3. Ask follow up questions to assess student understanding. A very handy request for teachers is, "So, could you repeat back to me, what I want you to do / what I said / explained?"
4. Speak less - decrease teacher talk time and let students have more opportunity for production rather than reception of language.
Of course there also is the age old, eternal problem us teachers struggle with - how to stop just going through the motions. You know, "I pretend to teach, students pretend to learn." How to make your self and your classroom and your students authentic, there, in flow and learning. Not just doing a dance that makes it appear so....
But the important thing to remember is to ask the question - "Do my students understand me?" and conversely, as a learner, to ask, "Do I understand?" Start from there and stop faking it - that is unless faking it provides some side benefits outside of learning. If you know what I mean......