Is there a specific age for the muezzin, and can children under the age of twelve call the adhan for prayer?

The jurists agreed that the adhan (call to prayer) of an undiscerning child is not sufficient, while they differed on the validity of the adhan of a discerning boy. The majority of scholars permitted it as long as he comprehends the adhan. The Malikis, however, held that his adhan is not valid unless he relies on an adult. Ibn Taymiyyah distinguished that the adhan which fulfills the obligation and is relied upon for prayer times and fasting should not be performed by a boy, whereas the adhan for an emphasized Sunnah can be performed by him. It is preferable for an adult male to perform the adhan to avoid disagreement, otherwise, the boy should rely on an adult.