Here is a link to a chart on blood pressure in children:
Average blood pressure for a 15 year-old is ~113/64, but this affected by height.
All the best,
Lisa Nelson RD
7 Natural Ways to Lower Blood Pressure
what about heart rate?
Here's a link that discussing heart rate and blood pressure in children:
Normal Heart Rate and Blood Pressure in Children
normal heart rate for 15 year old boy?