Sounds as though your concussions have started at the same time as your teaching career. Could it be that you are distracted by or overly focused on your teacher duties and not aware of the risk if hitting your head? Some people can get so focused on the task before them that they lose focus on the other issues around them. My wife is like this.

If this is your case, it sounds like you need to somehow, learn to be aware of your surroundings while you are focused on your teaching duties. It can be a challenge to develop the mindset to be more aware of your surroundings but it can be done.

There are methods of training your eyes/brain to be more aware of your visual surroundings. An occupational therapist may be able to help.