I’ve been taking a look at the Art of Problem Solving as a possible supplement to middle and high school math. AOPS has an impressive history and has developed a number of different media to support math instruction. I still think Khan Academy is excellent and find Sal’s video instruction to be clear.
Khan’s Singapore instruction (currently available for Grade 3) corresponds to the textbooks and workbooks available at singaporemath.com. At this time, Khan does not offer online exercises that match the videos directly. Most Khan Academy videos have no corresponding textbooks as Khan’s point has become the development of a system accessible from anywhere in the world.
The Art of Problem Solving curriculum looks especially promising to me. After teaching online classes for a year, the AOPS team decided that it is beneficial for students to have textbooks in addition to online materials. The level of detailed instruction in the textbook sample pages is impressive. And the textbooks are supported by a full solutions manual (not just an answer key).
The online problems I viewed on the Alcumus section of the website are extremely well documented. Upon submitting an answer (or even selecting the “I give up” option), Alcumus provides a clear explanation of the solution, the location of related readings in the textbook, and links to applicable video lessons.
One of the strengths of Khan Academy is the flexibility to jump in to finely target areas in which a student needs help. The Art of Problem Solving offers the structure of a textbook as well. For a parent who grew up with traditional instruction, the Art of Problem Solving provides a solid hybrid of text-based and computer-based learning to use with students.