What If ...

MrDwyer over at Teaching Paradox posted an interesting question the other day: What if schools were open 24 hours a day?

Today while I was thinking about my next unit and what I would do with it, I wondered if I could do some collaborative lessons with another class in the school (as long as the units meshed).

As I was thinking of that I thought of this question:

How would collaborating across age groups help (or hinder) learning?