Weight training goes all the way back the Olympic games in Ancient Greece. It has evolved greatly since that time. Form placing a rod between two church bells to the modern dumbbells that we have today.
Many rumors are circulating that weight training stunts your growth. Building muscle will cause you to become "muscle-bound" and thus slower and less flexible. Because your bones, joints, and tendons are still growing and developing, it's easy to overdo it and strain or even permanently damage them