Children exhibit a wide range of behaviors. Each has a different temperament and responds differently to his environment. One child can be shy and in need of encouragement at every step. Another might be boisterous and fearless, needing you to hold him back from doing everything that pops into his head. If abnormal behavior interferes with normal functioning, or if there is a marked change in behavior, parents and other caretakers should look into the causes.Abuse and NeglectIf a child's school performance suddenly deteriorates or if she starts acting fearfully or aggressively, abuse or neglect could be the underlying cause. Abuse can be verbal, physical or sexual. As the Child Information Gateway of the U.S. Department of Health and Human Services explains, the child might become abnormally compliant. She might appear to be always watchful, as though something bad is about to happen, and will shrink away when an adult approaches. She might be under-dressed for the hamattan and have poor hygiene. If a child exhibits highly sexualized behavior, or refuses to undress in the locker room after gym class, a distinct possibility of sexual abuse exists.BullyingIf your child is a victim of bullying, going to school might become a nightmare. A child previously eager to go to school might cry every morning and exhibit anxiety when it's time to leave home. A previously independent boy might start to cling to his parents. His school performance might deteriorate, and additional symptoms such as bed-wetting can appear. Bullying between girls is often verbal, though it can be physical, too. Boys tend to bully other boys using physical means. Your son might come home from school with injuries. He might not to want to explain them out of fear that if he reports the bullies, they'll only escalate their bullying.Sleep ApneaMChildren can suffer form sleep apnea just like adults, though the cause is often enlarged adenoids or tonsils rather than obesity. Sleep apnea leads to multiple awakenings during the night and sleepiness during the day. According to Stanford University, the child can become irritable or depressed. Learning problems may develop, along with deterioration in school performance. In the morning, he might appear confused. During the day, he might have difficulty concentrating. Sleep apnea can lead to a significant personality change.Seizure DisorderCertain types of seizure disorder can lead to changes in personality and behavior without the classic motor seizures. Partial complex seizures cause periods of altered consciousness with reduced awareness of the environment. During the seizure, the child may act oddly, may make repetitive movements or show aggressive behavior toward others.Absence seizures cause a brief loss of consciousness without any convulsive movements. The child can have multiple seizures during the day, but to the outside observer these will pass unnoticed--at most, she might appear to be daydreaming. Being absent in this way during much of the school day can lead to difficulty learning, irritability and other changes in behavior.Source: livestrong.com