So, after a very long delay, here is the draft language of the Creative Commons license option for permitting only educational uses:
You may not exercise any of the rights granted to You in Section 3 above except in satisfaction of both of the following conditions:
(i) You do so in a manner that is directly related to and of material
assistance to the primary teaching and learning activities of an educational institution, and
(ii) You do so solely for educational purposes.
An “educational institution” is a school or other organization primarily
and directly engaged in facilitating teaching and learning.
Rationale below. Please direct comments to the cc-education list.