George, in New Zealand, the situation was similar to the one you described. Teacher’s productivity was ‘owned’ by a school’s Board of Trustees, who govern the school on behalf of the state. This covered anything produced that had to do with the expertise or experience of the teacher whether in school or out. Special dispensation could be granted by application to the board (ie for those writing a book), or for the teacher to share, or remove the resources on leaving the school’s employment.
In recent years however more and more school are adopting a Creative Commons licence. http://creativecommons.org.nz/2012/10/the-original-creative-commoners-teachers-and-open-educational-resources/ My own school adopted such a position last year, which makes the entire process, far more transparent and manageable.
For students (and learning) the entire process was always far easier with students always regarded as the creators and therefore owners of their own productivity. To this end I have always had to seek permission from all students to hold and share assessment materials for moderation, even with external national assessment.