The teaching and community project in Jambiani, Zanzibar, promises amazing surroundings and a true impact on the local community. That is partly true, the site is beautiful and the locals are interesting and normally fantastic to interact with!
The African Impact organization on site have cute ideas for how to make an impact on the community. Cute, but not sustainable. This is a very good destination if you are an unexperienced teen and requires detailed schedules in advance which you don't need to plan yourself. When you feel that the possibility to take part has to be more important than the actual impact. Unfortunately, African Impact tweeks that picture a little.
I am a teacher, educated in environmental sustainable development and multiple times volunteer. My conclusion was unfortunately that none of the activities offered at the site today is actually sustainable. However good African Impact makes it all sound, it is not sustainable to fly in people from across the world to paint houses (when a local painter of course would have done a better job and get a job opportunity) or litter picking without continously involving the locals as part of a long term and well planned environmental project. There are even environmental activities that are called 'recycling', even though they don't actually involve any recycling. Neither is it sustainable to fly people in to teach subjects they are not educated to do. To teach English in an European school requires several years of university studies, but at African Impact in Zanzibar it is obviously considered a hobby. The locals in Jambiani deserves the same quality of education as everyone else and there is no reason to see their education as 'whoever, however'. A positive attitude and even good knowledge in English does not mean that you know how to teach it. As a volunteer project, which is a form of charity, the African Impact teaching and community project is to much Hakuna matata and not enough professionality. Charity is not to lure as many volunteers in as possible, it is to secure the quality by engaging people with the right skills or utilizing different skills for different parts of the project.
Above is simply my honest analysis of the project. If you think differently and believes this project is right for you, then make sure you ask African Impact for a detailed description of how your money will be used. Do that before you pay the deposit, since you have the right to know.