Good blood pressure readings for children depend on their age, height and gender, explains the American Heart Association. Generally, blood pressure is low in infancy and rises as children age, according to University of Rochester Medical Center. Boys have slightly higher blood pressure readings than girls.
For 3- to 6-year-old children, prehypertension systolic pressure readings should be between 100 to 113 mmHg for boys and 100 to 111 mmHg for girls, states the National Heart, Lung and Blood Institute. For 7- to 9-year-old children, prehypertension systolic pressure readings are between 106 to 118 mmHg for boys and 106 to 116 mmHg for girls. For 10- to 12-year-old children, prehypertension systolic pressure readings are between 111 to 120 mmHg for boys and 112 to 120 mmHg for girls.