Pros
Denis' School provides excellent support for their English teachers, including providing professional development for building better lessons and providing interesting teaching material as well as helping out with all things visa related. I highly recommend working at Denis School. I worked at DS almost 3 years and I had the opportunity to teach webinars as well as in person lessons, plus had the opportunity to write lesson material for ESL videos and business presentations.
Cons
The only cons are that sometimes you need to travel far for your lessons. There are also a lot of lessons that need teachers so you may be offered lots of classes, sometimes even on weekends. Be sure to communicate with the staff about how many you'd like to take on and what days you want to work.