A boy’s height of 126 centimeters at 7 years and 9 months is not short and is considered normal. According to the standard of “Evaluation of Height Development Rating of Children and Adolescents from 7 to 18 Years of Age”, the normal range of height is between -2SD and +2SD, SD is the concept of standard deviation, and those outside of these two ranges are considered to be of short or tall stature. In other words, a height of less than -2SD is considered short and a height of more than +2SD is considered too tall. The range of -2SD and +2SD for a 7-year-old boy is 113.51 to 137.46 centimeters, and the range of -2SD and +2SD for an 8-year-old boy is 118.35 to 143.08 centimeters. Therefore, a boy’s height of 126 centimeters at age 7 years and 9 months is not too short, and it’s within the normal height range. If your child is short or too tall you need to seek prompt medical attention for timely intervention and treatment if necessary. If you need to use medication, should be under the guidance of a professional physician, not blindly use their own medication, resulting in adverse consequences.