in boys following changes occur
Pubic hair growth -- as well as armpit, leg, chest, and facial hair -- begins in boys at about age 12, and reaches adult patterns at about 15 to 16 years.
Boys do not start puberty with a sudden incident, like the beginning of menstrual periods
Boys' voices change at the same time . Nocturnal emissions occur with the peak of the height spurt.
and in girls following changes occur
Pubic hair, armpit and leg hair usually begin to grow at about age 9 or 10, and reach adult patterns at about 13 to 14 years.
Menarche occurs about 2 years after pubic hair appear. It may occur as early as age 10, or as late as age 15.
Girls have a rapid growth in height between ages 9.and 14., peaking at around age 12.