Some members of my group have upgraded to Joy School 2.0, and I still have the old version. Can we use them together?

This is doable, but we don’t recommend it. It would take some organization on your part because the old and new curriculum do not easily match up. The new curriculum was redesigned to give a continuity to the Joy School days and a set schedule so that children are familiar with the routine. The old curriculum does not provide that, so it will somewhat negate the huge benefits of the new curriculum if you are also using the old one.