Why would an 11 year olds heart beat 121 beats per minute?

Children 1 to 10 years, normal heart rate is 70-120 beats per minute. Children 10 and older, normal heart rate is 60-100 beats per minute. A child's heart normal heart rate can vary, for example, a smaller child may have a slightly faster rate. A newborn has a normal heart rate of 100-170 beats per minute. Anytime there is a concern for your child's health you should discuss it with their pediatrician.