Who said "The greatest teachers are often the most demanding."?

This quote is attributed to Shifu.

The greatest teachers are often the most demanding. - Shifu

"The greatest teachers are often the most demanding."

Shifu Education

"There is no secret ingredient. It's just you."

"When will you realize? The more you take, the less you have."

"Your story may not have such a happy beginning, but that does not make you who you are."

"It is said that the Dragon Warrior will bring peace to the Valley."

"Education opens doors."

"Education opens doors to endless possibilities."

"I ain't got the education you got, bub."

"You can't put a price on history."