If you intend to teach deeply you will almost certainly be part of the process of causing pain to your student. You cannot teach without offering discomfort to your students. Some of them may truly suffer. The deeper the learning, the more likely this is. Why?
Learning is change. Change often brings discomfort. Learning is about moving between conceptual systems. It is at the edge of such systems where stumbles are most likely to occur, and these stumbles can hurt.
Sometimes pain is an indicator of a protected area. Sometimes these protections are essential and important and you as a guide and teacher must join with the student in protecting these areas. Sometimes these protected areas house great potential for new insights, and you as a guide and teacher must help the student see new ways to go through the border rather than go around.
If you are ill at ease with the idea that you might cause your student pain, even unintentionally, your teaching is handicapped; you will attempt to avoid causing pain and consequently avoid any teaching that might cause pain.
There are also teachers on the far end who believe that learning without pain is not true learning. These teachers are also handicapped; they will not be able to teach in ways that do not include discomfort or suffering.
Both extremes cost the student. If you teach your student that pain is always to be avoided, they will learn avoidance, they will seek easy paths, they will believe themselves to have failed when they hurt. If you teach your student that only pain can bring knowledge they will not be able to see the way in front of them unless it is painful.
In the service of teaching, both avoidance of giving pain and seeking to provide it are limited views. Instead see pain as information, as a signal of a stressed system, as a warning of a border coming, as a warning of potential damage.
If you look closely at your students, you will see the discomforts they endure daily. Why do we not see this? Usually it is our own discomforts that prevent us from seeing discomfort in others. Become willing to see their pain — which may mean a willingness to see your own — and then keep watching. Sooner or later you will see pain that you have had a hand in creating. This is a moment to keep your eyes open and your judgment soft so that you can learn.
Pain is individual and what hurts or damages one student will leave another one unfazed. In order to avoid causing pain or damage without good reason, you must learn the student, learn what hurts them, learn what might break them.
Look beyond the surface. Every child knows how to dramatize pain to gain attention or how to mask pain if they believe the cost to revelation is too great. Look behind the apparent. Listen to what is not said. See behind the presentation.
Again it is about listening and watching. First learn to see pain in your students. Next learn to see the connection between your teaching and that pain. Next, see what, if anything, the student learns in those moments, on those edges.
Study this as you teach. Your student’s reactions will show you where your teaching causes discomfort or pain. If you watch long enough and deeply enough you will start to see where the line is between pain and the start of damage. As you begin to learn this, your students will be safer in your care, and your teaching will be more effective.

[...] It is essential that you learn to see pain in your students. Even if you believe that pain should never part of your teaching, you should study discomfort and pain in your students to know what it looks like. Close your eyes to this and you lose the ability to make an active choice. Be knowledgeable and choose. [...]