Our first STEM Challenge of p3/4 was making marble runs using newspaper and junk.  We spoke about how to design it and what features a marble run would need.  My instruction was that it needed to be able to stand up on its own and a marble needed to be  put in one end and come out of the other.  Each group made an excellent marble run and they all went for very different designs.  We had a class vote to decide the winning group and it was Isla, Eleanor and Hendry!