I just wrote up a pretty long reply to a question of tortoise who's going to be TEFL'ing on the Galapagos later this year and thought it might be interesting to read for anyone else interested to go there (and an upfront PS: lease forgive me for any typo's made, I currently have a really crappy keyboard and sometimes letters just wont type!):
First things first... which island, which school? :). A lot of things depend a bit on the island but they all have their on unique ways.
Personally, i know and love San Cristobal the best. That's where i have been for 9 months. If you are teaching at a regular school, you will most likely be assisting in class, help out and hopefully have th chance to give your input and lead activities. If you'll be teaching at an after schoolhours school where children go to for additional English classes, count on being in full control (alone or together with fellow teachers depending on how many there will be during that time).
Full control means: come up with the lesson plans, use their books as guidance, improvise, lead the class.... everything! For me, that is the best and the worst at the same time. ;)
The children in the age group yo mentioned are like any other kid that age.... they dont want to be in school, especially not in an after-hours one when all of their friends are outside ;). This means you have to get creative to keep them coming!
Life on the islands is great! It is very easy to get to know and make friends with the Galapagueños. You can easily enjoy a pretty rich social life. Every island has it's bars and clubs to go out and learn Salsa or just to enjoy company of other people.
it is a relaxed life style, as can be expected on any small island! No matter where you will work, you will have time to enjoy the beaches, go snorkling, take up a PADI course, surf or visit other islands.
A bit about the islands: San Cristobal holds the capital (Puerto Baquerizo Moreno) and has about 12.000 inhabitants. Most people work in tourism and fishery. It has a great Malecon in front of the town where you can watch gorgeous sunsets, sea lions taking up benches, iguana's passing by and pelicans.The airport is located a mere 10 minute walk from town. The University of Quito (SFQ) has a spot on the island as well, GAIAS, right in front of a small beach (Playa Mann). The interpertation Center is a must see as it has a permanent exhibit about the human life and influence on the Galapagos. Behind it is a great snorkle spot, Las Tijeretas. There are many more places to see like Puerto Chino (beautiful soft white sand beach), La Galapguera (the tortoise breeding centre), La Loberia.
Santa Cruz is the most important island for tourism and trade. There zre about 20.000 or more living there with the most in Puerto Ayora. You can't fly directly into S. Cruz, instead you fly to Baltra and from there will be transported to Puerto Ayora on S. Cruz. Some attractions there: Tortuga Bay (a white sand beach that stretches pretty long), Charles Darwin Research Station (where you can find Lonesome George). Puerto Ayora is also the place to go if you need shopping with it's galleries and jewelrey stores.
Isabela is the most gorgeous with it's small town of Puerto Villamil, a real beach town with a very laid back atmosphere and sandy streets. The beach streches for 3 km in front of town. There are about 2000 people living on the island. Main attractions here are vulcan Chico and vulcan Sierra Negra which you can visit on a hike (4-6 hours) with a guide, Las Tintoreras where you can see and snorkle with pinguins and iguanas, Los Tuneles, Concha Perla, Muro de las Lagrimas.... and so much more!
Floreana is the smallest with 106 people permanentely living there. As it was the first human settlement in the Galapagos you will be able to find more human history here. The famous Postoffice Bay is here but you can only visit this while on a cruise!
All islands except floreana have a small hospital in case you need it (very limited equipd but free of charge).
Travel between the 4 islands goes by "lancha" speedboat ferries sort to say. Travel time between the island is 2+ hours depending on the condition of the sea. A one way ticket will normally cost $25,-
It is also possible to fly between S. Cristobal, S. Cruz and Isabela with a local airline, EMETEBE, that operates small 6-9 person airplanes. Travel time is apr. 30-40 minutes. If they consider you a local you can fly for the Galapagueño price, else you pay the more than twice as high foreigner price.