Kids And Martial Arts
Many parents enroll their children in martial arts classes because they think it will instill in them a structure of respect and discipline. Children learn to respect the teacher, other classmates, themselves, the training, the need to practice, and, at the same time they are exercising, which keeps them healthy.

The National Association for Professional Martial Artists, a professional association for Martial Arts club owners even has a program to help their members set up training for pre-school children. Clearly, starting kids in martial arts training can start as early as 3 or 4, and, once started, you can keep going all your life.
Kids who choose to give up martial arts in favor of base ball or basket ball will have benefited from all the physical training they have undergone and will be ahead of the game when it comes to strength, coordination, agility, and endurance.
So, however you look at it, starting your kids in martial arts at a young age will benefit them for a lifetime.