The reproductive system of a child is not mature. It needs to change as a boy or girl develops into an adult, so that the system is fully working. The time when the changes happen is called puberty.

Most girls begin puberty between ages 8 and 14, with an average of 11. Girls develop more quickly than boys and most finish puberty within four years. Most boys begin puberty between ages 9 and 14, with an average of 12. Most boys finish puberty within six years.

The changes happen because of sex hormones produced by the testes in boys and by the ovaries in girls. Some changes happen in boys and girls, while others just happen in boys or girls. Here are some changes that happen to both boys and girls:

  • underarm hair grows
  • pubic hair grows
  • body smell gets stronger
  • emotional changes
  • growth rate increases
Graph shows that height increases as age increases, there is a bigger variation of heights - at age 16 heights range from 140cm to 185cm. Boys are generally taller than girls, except for the ages 12 and 13 when girls are taller than boys.Girls and boys grow at different rates as they mature

The time between puberty and adulthood is called adolescence.


Here are some changes that happen only to boys:

  • voice breaks (gets deeper)
  • testes and penis get bigger
  • testes start to produce sperm cells
  • shoulders get wider
  • hair grows on face and chest


Here are some changes that happen only to girls:

  • breasts develop
  • ovaries start to release egg cells (the menstrual cycle starts)
  • hips get wider
Move on to Test