Many people like to read before going to bed, as reading makes them feel sleepy. The reason for this is that reading has an almost hyponotic effect on a person, as it involves rhythmic eye movement, a relaxed postion, and focused attention.
Your body becomes passive, you become less alert, and start feeling drowsy. if your reading involves mathematical calculations and deductive reasoning, your mind has to work hard too, and this can make you feel tired and sleepy as well. A useful tip- if you get sleepy while doing your schoolwork, don;t lie down and study. Sit, straight and take a little walk whenever you feel yourself nodding off!