Pros
After substitute teaching for Kelly Services from 08-12 until 01-14, I was blessed by the principal of a school I had done a lot of sub work for, with a permanent, full time staff position! Kelly Services was a joy to work with, and they have many of their processes online, W-2 access, pay stub, etc., so you don't have to wait for someone else to process items for you. The Flowood, MS office is the office I worked out of and there were very few times where I did not work 40 hour work weeks, I stayed fairly busy! If you apply yourself, be professional at all times, be on time for assignments, develop good working relationships with the administrators for the schools you'll work, good things can happen!
Cons
Medical insurance wasn't much to brag about, but fortunately, my husband's job takes care of that for us.