I chose Thailand Teach after months of surfing around the net. There is not a lot of local-based organizations that would allow students under 18 to join. And since my personal philosophy prohibits me to join the programs created by all those large international organizations that cost a fortune (I believe that organizations like those have their own interest in mind, generating money through creating volunteering opportunities), I looked for local ones like Thailand Teach.
With a Thailand Teach, I could really see that all the past volunteers, their efforts and donations are put to good use and that none of it is put into the pockets of the organizers. And through their Facebook page, I could see how the past volunteers all seem close to the host and happy in general with their experience. Lastly, through my interaction with Robert between emails, I began to really trust them since he is so responsible and thorough with every detail and plan.