No teacher or administrator should use or support the use of Khan Academy videos without watching the first episode of Mystery Teacher Theater 2000 or MTT2K.
Khan Academy teaches only one part of mathematics—procedures—and that isn't the most important part. Writing about mathematics, developing a disposition for mathematical thinking, demonstrating a conceptual understanding of mathematical topics are all more important than procedures. That said, procedures are still important, and Khan Academy provides one venue where students can learn them. In the end, I think every young person should have an account there. Even if only one in a thousand or ten thousand benefit, that would be a terrific outcome.