Cons: compensation, high-stress environment, unsupportive administration
As a long-term substitute, I had the same expectations and duties as contracted teachers without the pay and benefits. I consistently worked well past contract time and spent my weekends grading papers and lesson planning. I also had to buy supplies for my own classroom after the teacher who was there before I was up and left mid-year, taking everything. Administrators provided little support to teachers and kept consistently disruptive students in the classroom who should have been removed and placed in an alternative environment. Administration seemed more concerned about appearances, in other words, test scores, than students' and teachers' well being. And don't even get me started on the proficiency exams. Students were so stressed and upset over these exams. A few were in tears on exam day. I'm all for assessing students, but this level of high-stakes assessment is just ridiculous. The majority of my students read well below grade level, yet I was expected to teach them at high school level. Overall, it was a frustrating job. The only thing I truly loved about it was my students. They were fantastic.
I have been a short-term sub as well, and the flexibility is great. The pay is okay. If the teacher you sub for has an Early Bird class or no prep, you don't get paid extra. A 5.5-hour assignment and an 8-hour assignment can have the same pay, depending on the school. Also, more schools should be paying their subs at the higher ($110) daily rate because the amount of work warrants it.