The standard height of a nine-and-a-half-year-old boy should be between 126.7 cm and 149.4 cm, and his weight around 30.75 kg. However, due to individual differences, the actual height and weight are related to nutritional status, hereditary factors and physical activity. 1. Nutritional status: Nine-and-a-half-year-old boys are usually 126.7 centimeters to 149.4 centimeters tall and weigh about 30.75 kilograms. If the child has been partial to food or picky about food for a long time, it will cause malnutrition, which will lead to a height and weight below the standard value. You can give your child more high-protein food, such as eggs, lean meat, milk, etc. You should also supplement trace elements as well as vitamins, and you can eat more fresh vegetables and fruits. 2. Genetic factors: If the parents are tall, the child’s height may also be higher than the same age, but if the parents are not tall, the child’s height will also be lower than the normal value. 3. Exercise: You can participate in outdoor exercise appropriately to stimulate the pituitary gland to secrete growth hormone, which will help children’s height increase. In addition, outdoor exercise can receive sunlight, and the ultraviolet rays in sunlight can promote the synthesis of vitamin D, which in turn can promote the body’s absorption of calcium and phosphorus, thus promoting the growth and development of bones. It is important to monitor your child’s height and weight on a regular basis, and when it is lower than the height and weight of the same age group you can go to the hospital, look for the cause and make improvements.