The sequence of some major events of puberty: This chart shows the ages at which some important changes of puberty occur in the average boy and girl. The numbers below each change show the range of ages at which that event begins. Notice that girls are on a slightly earlier timetable than boys, that boys’ height spurt occurs at a later point in their development, and that there are dramatic differences from child to child in the timing of puberty.
Data from: Tanner, 1978, pp. 23, 29.