Martial arts, as a whole, cannot teach anything except discipline, fitness, and focus. Ultimately, the most effective form of self-defense is simply being fit enough to run away. Any actively aggressive actions could result in a plethora of things, of which likely include personal bodily harm or potential legal repercussions. No amount of martial arts training can stop a bullet or make it sensible to take on someone with a knife.
Martial arts develops early on muscle development which can be beneficial for careers that require a modicum of physical labor. Many entry level jobs that are available in the U.S right now require a form of lifting or movement which is made easier when you have already began developing the innate and nearly subconscious skill of lifting early on. One of the causes for back pain in adults comes from improperly lifting heavy objects, which they do simply because they do not know how to.
Self-reflection or awareness is another important talent that many developing minds are not taught to do normally. Whenever they submit an essay the teacher tells them what is wrong with it and they may or may not comply with the advice that the teacher is giving them. This is not a form of self-awareness which is beneficial for children, this is merely informing them what they did wrong. Most medium-high level jobs require constant self-improvement. Looking at what one just did and reflecting on it. Constantly asking internal questions like "was that the best way I could have done it" or "is this what will sell" rather than having someone tell them.
Much of sports martial arts helps prepare children for early-on socialization skills. Many drills in martial arts require partners, including sparring or other forms of drilling. These team-building exercises insist that teamwork is required in order for both parties to succeed. Developing this talent, along with others, helps prepare future generations for the inevitabilities of work.