Too few books or too many? What is the problem in Taiwan?

This interesting story caught my eyes this summer when I read in the Taipei Times when it was published…

Most teachers use materials banned by MOE, poll shows

Nearly 70 percent of junior high school students said they have been taught with alternate “reference” books in class despite a ban on such publications, a recent poll showed.

“This result indicates abnormalities in our education system, as ‘credentialism’ is still hurting Taiwan’s junior high students,” Shih Ying, chairman of the Humanistic Education Foundation, told a press conference yesterday.

It boggles the mind: what the heck are ‘unauthorized’ textbooks? What is credentialism and how does it relate to this story? From what I’ve seen of school textbooks, schools rely on particularly few textbooks for outside reading, and too many for classwork.