They are no concentrate our eyes must have time in which to work, they must listen to the teacher's ear, and if done at the same time to make it work might not be as good as it should be and learners do not understand.
They can not concentrate because we have to look at the work at hand was to write. Ear to listen to the teacher And if done well, will make the job might not be good enough now to know it, too.
They are not distracted by the eye, we must have the task at hand is to write, your ears to listen to the teacher. And if together to get the job may be as bad as should then don't know about.