12-year-old boy dozing off in class for many reasons, may be physiological factors, neurasthenia, episodes of sleepiness and other factors. 1. Physiological factors: such as staying up late at night for a long time, not enough sleep, in the daytime classes will doze off, belonging to physiological factors, should ensure adequate sleep, dozing in class will disappear on its own. 2. neurasthenia: prolonged sleep deprivation or mental and psychological stress, anxiety, may lead to neurasthenia, will make the child doze off in the daytime class, may also be accompanied by dizziness, inattention and other symptoms. 3. Episodic sleeping sickness: may be related to genetic, environmental factors, infectious factors, will lead to the child in the daytime often appear dozing phenomenon, may also be accompanied by memory loss, restless sleep at night. 12-year-old boy dozing off in class may also have other reasons, it is recommended to go to the hospital in time, improve the examination to clarify the cause of the disease, under the guidance of the doctor to give targeted treatment or treatment.