Khan Academy just added an Android app to go along with its existing iOS app. Download from Google Play and check it out. This is the future of learning, where the emphasis is placed on learning and not what the “education establishment” considers “education”. What I mean by that is that “professional educators” all too often are mostly concerned with two things. First, they want to keep the “education club” exclusive, optimizing their wages and job security, but not student success. Second, they emphasize testing as a way to rank students, not as a way to improve learning. There are exceptions of course. Khan Academy is one. For more on this subject, get this book.