When an intelligence test is given to a child, if the level of the intelligence test is between 90 and 120, the child’s IQ mostly falls within the normal range. If a child’s IQ test score is below 90, he or she falls into the category of low intelligence. In general, the causes of low intelligence in children are divided into the following areas: first, due to congenital developmental backwardness. Second, if the child has brain damage and other genetic metabolic diseases, the child’s IQ is often very low as well. Again, if a child has congenital hypothyroidism, this can also lead to a poorly developed nervous system in the child’s brain, resulting in a low IQ. In addition, if a child has an IQ score of over 120, he or she has a high IQ condition. This condition is very beneficial for children’s learning as well as their lives.