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.
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.