The teenage years are a time when your child learns higher-thinking skills and puts them into practice to gain a sense of independence. Not all teens hit milestones at the same time, but virtually all teens reach certain milestones that show they're coming into their own.
In the teen years, most children go through a developmental growth period where their bodies become more like adults. Both boys and girls will start to grow pubic hair and armpit hair, and both should see significant growth in height. Girls will start to develop breasts and start menstruating. Boys will see growth in their penis and testicles and their voices will deepen. Typically, this process finishes by age 16 or 17, according to MedlinePlus.
Teens start to focus on romantic relationships. Many will have a first boyfriend or girlfriend, but even if that doesn't happen, the teen is likely to develop crushes on others. Many teens will also become sexually active, though some will wait until later in life to begin having sex.
In growing into an adult, teens begin to seek out independence from the family. This can manifest in rejection of parental ideas and rules, placing a higher priority on friends than family and seeking "grown up" experiences. First jobs and getting a driver's license contribute to this feeling of independence. Parents can encourage this by giving the child more responsibilities in response.
All teens must think about what they plan to do in the future. Few people know exactly what lies ahead, but many start to make plans and take the actions necessary to reach those goals. For some people, the path includes college; for others, learning a trade or starting a job. What the child does is not as important as knowing that there should be some plan for the future and learning how to break that goal down into achievable steps.