Draug and ck, its a little of both. Teachers don't "shut down," they only work less. Lesson plans need to be made, new standards learned, supplies obtained, professional development attended, scheduling done, class rosters drafted, classrooms cleaned and reset, etc. Teachers will always take a few well deserved weeks off in the summer, but there is always something that needs to be done, especially now that states are implementing Common Core and APPR.