The NCREL Policy Brief Professional Development: Changing Times (1994) discusses the importance of professional development:
Traditional inservice programs are designed around this skill-based, 'teacher-proof' curriculum. Not only do they assume that transfer of knowledge from experts to teachers is sufficient, but they also assume that teachers have little need to collaborate across subject areas or grade levels. In contrast, an interdisciplinary curriculum that emphasizes holistic thinking demands integration across traditional subject and grade boundaries. Schoolwide improvement and reform requires school faculties to work as a unit, not simply as a collection of independent artisans.
The emerging content standards codify this new definition of learning into expectations for all students. Standards alone, however, cannot reform education. Setting standards without providing teachers with time to study, implement, and reflect upon them is likely to lead to another failed effort. . . . Therefore, as the standards are developed we must simultaneously restructure school time to support ongoing professional growth.
Meanwhile, as ideas about schooling have changed, so have the demographics of the teacher population. Early retirement programs are encouraging many of the more experienced staff to leave the profession, creating a large new group of less experienced or induction-level teachers. The wide range of experience from newer teachers to those who have been teaching for quite some time also creates differing needs for professional development."