No two children grow at the same rate.
Although there are milestones that all infants should hit around the same age, stages of physical development get more broad as children get older. Children grow at different rates, so parents shouldn't worry if their child is a little taller or shorter than his peers. If he is significantly outside the norm or seems to stop growing and developing suddenly, consult a pediatrician.
Babies
By the time a baby is 3 months old, he should be able to lift his head while lying on his stomach. He should also be able to kick his legs while lying on his back and should be able to open and close his hands. By the time he is 7 months old, he should be able to roll over and keep himself in a sitting position without help and in a standing position with help. By the time he is 12 months old, he should be able to crawl, sit up on his own and pull himself into a standing position.
Toddlers
By the time a child is 3 years old, she should be able to walk and run. She should also be able to kick and catch a ball and stand on tiptoe. A toddler should also be developing muscles that let her hold in her urine and might be starting to use the toilet regularly.
Preschoolers
By the time a child is 5, he should be able to walk up and down stairs using alternating feet. He should be able to walk and run smoothly and climb up and down from structures such as playground equipment. A preschooler should also be able to ride a tricycle and bend over without falling. He should be able to control his pelvic muscles and should be able to primarily use the toilet, although he might still have occasional accidents.
School-Aged Children
Once a child enters middle childhood, which is generally considered to be from about 5 to 13 years old, she will grow an average of two inches a year and gain an average of 6.5 pounds per year. She also might have a growth spurt between 6 to 8 years old; these averages apply to boys and girls.
A school-aged child should also get increasingly stronger as he gets older and should show increasing coordination in exercises like catching, throwing and running. Puberty begins in girls around 10, and they might start menstruation as early as one or two years later. Boys typically start puberty around 11, and they might have another growth spurt around this time.
Teenagers
Puberty continues into the teen years, so a teenager might continue to grow rapidly in his early teens. A boy's voice might grow deeper, and a girl's breasts will grow and she might start menstruating in her early teens if she hasn't already started. As hormones fluctuate, some teenagers will get acne. Most children will stop getting taller as they reach their late teens, although some will continue to grow into their early 20s.
Tags: should able, should also, able walk, also able, months should, months should able, should able walk