How should teachers deal with fatigue in the classroom?

One part of dealing with fatigue in the classroom is helping teachers feel more energized. To this end, researchers such as Sapienza, Crandell, and Curtis have examined the use of sound-field frequency modulation (FM) amplification in the classroom to lessen the strain on teachers' voices. The data have supported the use of FM amplification to lessen teachers' voice fatigue. (Please the NIH link below.)

To deal with student fatigue, studies such as that done by Dowson called "Do children learn better in the morning or afternoon?" (see the link below) suggest that some students, such as teenagers, actually learn better in the afternoon. Their circadian rhythms fall in the morning and from 3-5pm in the afternoon, and they are most alert in the later morning and early afternoon, so harder lessons should be planned for this time. 

In addition, students who are more interested in what they are learning tend to be more alert, according to research done by Berto et al. (2009). This research was published in an article called "An exploratory study of the effect of high and low fascination environments on attentional fatigue" (see the link below). Students can remember more when they rate subjects as highly fascinating, so teachers need to build elements into their lessons that are likely to catch students' attention and keep it. That means avoiding repetition or predictable lessons.