When children start school at age 5, many are about 43 inches tall and weigh about 43 pounds, according to Drugs.com. During puberty, a child's height and weight increase rapidly. Children who have started puberty reach about 59 inches tall and weigh about 90 pounds by age 12, on average.
Growth rates for children depend on the age at which they start puberty, their diets and their genetic height, explains the American Academy of Pediatrics. During middle childhood, most children grow about 2 inches per year. They gain about 6.5 pounds per year. Children grow at a slightly increased rate between ages six and eight.
During puberty, children start to develop public hair, armpit hair and body odor, notes the AAOP. These changes are accompanied by a drastic increase in weight and height. About 25 percent of a child's growth happens during puberty. Girls are typically taller and weigh more than boys before puberty, or in the early years of puberty.
As boys finish puberty, they become taller and heavier than girls, on average, according to the AAOP. Boys grow up to 4 inches in a year, and increase their heights anywhere from 13 to 14 inches in four years. They increase their weight by as much as 40 pounds in four years. Girls grow up to 10 inches and 25 pounds over the course of their childhood. They grow as much as 3 inches in the year before they have their first menstrual cycle.