Answer:
Any. Most popular I've seen as whole school productions are:
Rata and the waka.
Uenuku and HInepukohurangi.
Tutanekai and Hinemoa.
Te Aohurhurhu
I always had a soft spot for the maori legends of tribal mountains. Take for instance the legend about Tarawera, Putauaki and Whakaari. A love triangle that is always a great heart pulling story to depict in modern times such as these.