I agree that parents will take kids out of school if they get a really good deal, at least some of them will.
For example: My husband and I went to WDW the first week of September when the DP was just initiated! My TA said that it would be a great time to go because no one would take their kids out of school the first week of school! Well, was she ever wrong! We were amazed at the amount of families with kids in the parks. The DP drew them out of the first week of school, and continued to be a draw for people from then on! We used the DP for a couple of years til we found out we spent less and were happier without the DP.
So, I wouldn't be surprised at all that parents take their kids out of school (and I'm saying some parents, not all) just to go to disney.