Adolescence is a time of various growth spurts for both boys and girls. Girls will do a lot of their growing fairly early during the course of their puberty. Their growth spurt can begin anywhere from age 9 through 14 years old. The best way to gauge when to expect a girl's growth spurt is based on when she begins puberty, which is generally first signaled by the development of breast buds. Girls will likely reach their full adolescent height by the time they're 12 years old. Assess your girl's growth relative to when her puberty did begin; if she is a late bloomer, her growth spurt will likely come late as well. When teen girls do grow, they increase not only in height, but they will see their body fat increase as well. Not to worry -- the increased body fat is what accounts for newly rounded hips and growing breasts.
Boys go through various phases of growth spurts, accounting both for their height and increased muscle mass. Their first growth spurt will occur early in puberty, usually around 10 or 11 years old. Again, this first growth spurt will usually occur in tandem with their other first signs of puberty, such as an increase in the size of their testicles. After they go through this first growth phase, boys will usually have a second growth spurt roughly two years after their puberty has begun. "Spurt" may not be the right word, as this growth phase lasts for two to three years. This growth phase is when teen boys will achieve the largest portion of their teen growth; it's also when boys will start developing greater muscle mass, and their shoulders will widen. Toward the end of puberty, boys will have a final growth spurt, which will bring them to their full adult height.