One of the many education NGOs in the city, the Akanksha Foundation gives you the chance to educate children who have little or no access to primary education. There have been several success stories to have come out of Akanksha including that of a roadside bookseller, who is now in the United States studying to be an entrepreneur.
What You Can Do: Akanksha has centres both in Mumbai and Pune and they are always looking for teachers. Note, you will also receive training before interacting with the kids.