Yes, all to be teachers need to work as a sub at the specific district before he/she becomes a teacher there. I've been working as a sub for 2 years now and yes there are positive and negative aspects of it. The positive ones would be moving to different schools and meeting new students. The negative ones would be middle schoolers including six graders. Luckily I am single and only use the jobs to pay rent. I'd taken most of the credential courses but most are a joke especially ones that require writing a verbatim teacher/student lesson plan. I just need to decide whether to stick to it and pass my R.I.C.A or go back to whatever I was doing as an undergrad. I think you wasted your money at the University of Phoenix for getting your Master's--you should have gotten it after getting hired. Teachers are like artists/musicians...it takes us a long time to "make it". Don't worry because by 2016 or somewhere in the near future, tenure teachers will retire. The only other way out is to work for a private school. I know most teachers are working in San Bernardino County (east of the 10).