In the past year, education-reform icon Sal Khan has been lauded by Bill Gates as the "teacher to the world" and has been listed among Time magazine's 100 most influential people.
His Silicon Valley-based Khan Academy posts free videos -- most of which star Khan himself -- and offers accompanying questions on everything from addition to calculus to art history. As of this month, Khan Academy had tallied more than 177.2 million views of its lesson pages and is being used by traditional and charter schools, as well as individuals worldwide.
Amid the adulation, some teachers now have piped up with criticism of his teaching methods. While they admire the website's accessibility and fun, the question sets and teacher "dashboard," they criticize lapses in content, a shortage of explanation and occasional leaps in logic. And, they say, the collection of eight- to 10-minute videos skips the heavy-lifting part of teaching, focuses on procedures over concepts, and doesn't ensure that students