[dsr_]

Probably because those are the six methods that cover 99+% of the kids. Picking the one best method, which may only cover 30%, isn't enough.

Or did you think everyone learns best the same way?

[lazerwalker]

Do you think that 99+% of the kids learn best by reading a textbook?

[homosaur]

Absolutely not, but you have to make that textbook as relevant as possible to the widest population if you're going to require its usage.

[greedo]

Time is money, even in the classroom. If you spend time teaching x four different ways til Sunday, the kids have no time to master any singular technique.