I have actual proof that there are thousands of teachers working diligently throughout the summer. I work for PBS TeacherLine and we provide online professional development courses to PK-12 educators. Currently, our summer 2009 term is the highest enrollment we have had in our national courses during the past 5 years...over 2,500 teachers are taking 6- and 10-week long courses that are rigorous and worth 2-3 CEUs and/or graduate credits. So there is absolute proof to back up your claim.
Now, if you'll excuse me I'll be getting back to the pool ;)