NPBPAF
National Pediatric Blood Pressure Awareness Foundation
Did you know that blood pressure values are very different for children as compared to adults?
BP values for children vary depending on age, gender, height, and weight.
Below is a simplified abnormal blood pressure screening table. This is information obtained from David C. Kaelber and Frieda Pickett and was published in an article from the Official Journal of the American Academy of Pediatrics.

Who should be taking blood pressure measurements for children? Children who need blood pressure screens: For a child to be given a diagnosis of hypertension, they must have three separate elevated blood pressure readings. One elevated measurement does not necessarily mean your child has high blood pressure. However, it is enough to warrant having additional readings to rule out hypertension.
If your child's healthcare provider does not routinely take their blood pressure, don't be afraid to ask. Your child's health is important enough to speak up. The NPBPAF is working hard so that one day soon it will not be up to you to ask. It will be done automatically just as height and weight are.