In elementary school, look at how much time they actually spend learning. Take out time to unpack and repack backpacks, lunch, the time spent on the morning announcement, snack (if the still do it), gym, art or music, trips to the bathroom, recess, and all the time spent having 25 or so kids move from one activity to another. How much time is really spent learning each day? Two to three hours maybe??
I think if the parent takes the time to make some work out of it it can be deemed educational. Adding up receipts at the end of the day, writing a paragraph (or a page) on what you did, read a guide book and make an outline of what you want to do in each park, make a budget for souvenirs, stuff like that. Will most parents do that? No, but if they do they can turn it into an educational vacation.