At 11 years of age, the "normal" blood pressure range is close to the same as it is for an adult.
Generally speaking, the normal blood pressure range for an 11 year old boy or girl is around 115/75 to 125/85 or thereabouts.
However, this range can vary depending on many factors, such as the fitness level of the child. A skinny kid who plays a lot of soccer probably will have a lower blood pressure than a larger kid who isn't very active. In that respect, blood pressure in children isn't much different from blood pressure in adults.
If you have concerns about your child's blood pressure, you should consult your pediatrician.
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