When you have un clase -----------(dormirse) porque es uninteresante. The question wants you to conjugate dormirse correctly and use it reflexively. Would it be se duerme or se duermen.?

Collective nouns, like "La clase", take singular verbs in Spanish, so it would theoretically be "se duerme" and NOT "se duermen". However, the sentence in the question does not make much sense. If the sentence was supposed to be "The class falls asleep because the teaching is uninteresting", it would be "La clase se duerme porque el enseñamiento no es interesante."