Kids need a good experience on supporting themselves and making money without mom there to help. I'm not saying work as a teacher but a fast food worker or a department store clerk is a really good start and will help the kids learn. It will also make them independent and teach them the skills needed to work. Also they will be off those gosh darn videogames!
I think that four-teen year old should be able to get a job so they can get a head start on getting money for college, a house, food, and other things. Having jobs might make them a little more responsible over all their actions and their decisions. Even if they can't stop some habits, they can still get a job.
Most teens will not have the maturity to hold a job because the might screw around doing things they are not supposed to do. Also they will need time for homework or other after school activities they do like sports or boy scouts. I believe this would not be right to let them have a job.
Studies show that a brain isn't fully developed until the child is an adult. On the job, in a dangerous situation, kids might not know what to do. Being only 14, they might not have had experience with situations like a robbery, etc. Also, 14 year old's might not be fully mature yet. High School is where people get serious, and 14 is the age of an 8th grader. I just don't think it would be a good idea to let kids that young work.