text: I suppose there could be a requirement to serve in problem areas but I suspect this would serve as a disincentive and make the teacher shorter worse.
  There are a lot of problems associated with the one teacher in a primarily age based grade level structure. This problem is greater in a rural area where there are few students in a class. If there is a small class size and only 1 or 2 students who might want advanced topics like physics or calculus it is expensive and difficult to justify 1 class and one teacher so those students can receive important instruction.
  1st year teachers are frequently ineffective and need supervision from a more experienced teacher. By using a system with a master teacher who helps teachers while having the ability to deal with advanced or special instruction a lot of both poor instruction can be avoided as well as better being able to use local talent or people who have not spent the time and money needed for complete certification.