There's a common belief among inhabitants of American bureaucracies that expertise does not exist, only knowledge, so if that knowledge can be written down then there's no need for training or experts. Many people in HN have likely encountered middle-managers who ask their senior engineers to write policies, and then hire teams of juniors to implement those policies rigidly -- same principle.

When applied to education, this manifests as a belief that the teacher is less important to education than the textbook. The people writing the educational policy framework might understand that it's not a one-size-fits-all, but they're not allowed to write one policy per child. The teachers in a classroom environment aren't given the autonomy to teach according to their own judgement, because (in the eyes of the administration) if their judgement could be trusted then they would be writing policy instead of teaching.