Middle adolescence is a time of blossoming development — the insecure, inwardly focused 13-year-old becomes a cheerful, charming 16-year-old looking toward the future. During this period of adolescent development, your child’s thinking skills take a decidedly adult turn, their body matures, and friends and social networks outside the family become increasingly important. Now is when you will really begin to get a glimpse of the adult your child will become.

Physical adolescent development

Boys and girls still exhibit markedly different levels of physical maturity as they enter middle adolescence. Girls’ rapid growth is generally tapering off, while many boys have yet to see the beginning of their much-anticipated growth spurt. By the end of this period, most girls will be near their adult height; boys may continue to grow until age 18 or 19.

Everyone goes through puberty at their own pace, so don’t be alarmed or if your teen develops faster or slower than others.

Physical development girls ages 13 to 16

Girls go through puberty in a series of events, often before boys of the same age. Every girl might go through the changes at a different time. These are average ages when puberty may happen:

  • First puberty change is breast development. The breast and nipple elevate and the dark area of skin that surrounds the nipple gets larger.
  • Pubic hair appears shortly after breast development. Public hair thickens, darkens, and takes on adult triangular pattern.
  • Hair under the arms appears at about 12 years old.
  • Menstrual periods start between 10 and 16 1/2 years old. Menstrual periods become regular; ovulation is established; pregnancy becomes possible.
  • Growth spurt tends to happen at 13 years old; adult height is reached between ages 14 to 17.
  • Hips widen; fat deposits in buttocks, legs, and stomach increase.

Physical development boys ages 13 to 16

Boys also go through puberty in a series of events, often after girls of the same age. Every boy might go through the changes at a different time. These are average ages when puberty may happen:

  • First puberty change is enlargement of the testicles.
  • Penis enlargement begins about 1 year after testicles begin enlarging.
  • Pubic hair appears at about 13 1/2 years old.
  • Ejaculation and wet dreams (nocturnal emissions) start at about 14 years old.
  • Rapid growth in height and weight; reach full height between ages 16 to 19.
  • Muscles fill out and strength increases dramatically.
  • Voice deepens.
  • Hair under the arms and on the face, voice change, and acne at about 15 years old.

Both girls and boys

  • Often/always hungry; appetite is great.
  • Need for sleep increases; may sleep quite late on weekends.
  • Sweating increases.
  • Rapid growth may cause clumsiness and lack of coordination.
  • Sexual desires and fantasies increase.

Intellectual adolescent development

Between 13 and 16 years old, your child’s ways of thinking about themself, others, and the world shift to a much more adult level. They enter middle adolescence with a focus on things they can experience here and now, and move toward being able to imagine the range of possibilities life holds. Every child progresses at a different rate. Here are some of the changes you can expect:

  • Arguing skills improve (and are demonstrated often and with great passion)
  • Reasoning skills improve.
  • Develops the ability to apply concepts to specific examples.
  • Develops the ability to think abstractly.
  • Becomes interested in politics and social issues.
  • Starts to set personal goals and think long-term.
  • Compares themself to peers.
  • Learns to use deductive reasoning and make educated guesses.
  • Learns to reason through problems even in the absence of concrete events or examples.
  • Becomes able to construct hypothetical solutions to a problem and evaluate which is best.
  • Begins with a present focus, mixed with some fantasy.
  • Learns to recognize that current actions can have an effect on the future.
  • Starts to set personal goals (and may reject goals set by others).
  • Decision-making skills improve.
  • Begins to independently differentiate right from wrong and develops a conscience.
  • Learns to distinguish fact from opinion.
  • Learns to evaluate the credibility of various sources of information.
  • Becomes able to anticipate the consequences of different options.
  • Likely to challenge the assumptions and solutions presented by adults.
  • Develops more empathy.

Social and emotional adolescent development

During middle adolescence your child will continue to be an emotional pendulum: happy and at ease one year, troubled by self doubts the next. These swings will smooth out as your teen approaches the end of high school and gains more confidence in their own independence.


  • At times uncertain, unhappy, and sensitive.
  • At times withdrawn, spending a lot of time alone; needs privacy.
  • Convinced that everyone else is watching and judging.
  • Very concerned with body image, looks, popularity, and clothes.
  • Self-esteem at a low ebb.
  • Not sociable with adults.
  • Friendships tend to be group-focused; there’s often more squabbling than a year ago.


  • Generally happy and easy-going.
  • Recognizes own strengths and weaknesses.
  • Finds many faults with, and is embarrassed by, both parents.
  • Likes to be busy and involved in many extracurricular activities.
  • Social circle is large and varied; includes friends of both genders.
  • Very anxious to be liked.
  • Interest in the opposite sex (or same sex, or both) is strong.


  • May be quarrelsome and reluctant to communicate.
  • Strong desire for independence; wants independence from family.
  • Relationship with siblings may be better than with parents.
  • Friends are very important; may have one or two “best friends”.
  • Dating and romantic relationships are commonplace.


  • Relationship with family is easy and giving.
  • Feels comfortable in own skin; secure sense of self.
  • Starts to view parents as people, rather than rule-makers.
  • Friendships are very important.
  • Most have many friends of both genders with shared interests.
  • Romantic relationships can be quite intense.

And finally …

Remember that adolescent development is influenced by many factors — genetic, social, and cultural — and each child is an individual who will develop at their own pace. The milestones presented here are averages; your child may progress more quickly or a little more slowly. In the U.S., these averages are changing as well linked to obesity, stress, and environmental chemicals. You can help your child through this period of great change by showing support and listening to their worries and concerns. And as always, if any aspect of your child’s development seems atypical, talk to their pediatrician and encourage your teen to ask questions as well.


  1. The Growing Child: Teenager (13 to 18 Years) Stanford Medicine Children’s Health
  2. The Growing Child: Adolescent 13 to 18 Years John Hopkins Medicine Health
  3. John P. Dworetzky, Introduction to Child Development, 5th ed., (West Publishing, 1993).
  4. Kids and Teens: Developmental Milestones John Hopkins Medicine Health