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The school was chosen to be on the Shotover River beach at Arthurs Point to make up for the disappointment after bad weather prevented Prince William visiting the school when in New Zealand in 2005.
Two teachers, Janey Winders and Joelle Healey, will accompany the pupils on Sunday.
Mrs Winders said the pupils would be learning about ''the Royal Family and etiquette and what it means to meet a duke and duchess''.
Kate Edmunds (10) wrote to her teacher outlining why she should be one of the chosen 15 and said she was ''really excited and nervous about meeting them''.
Annabelle Jones (11) said she had been practising her curtsy so she was prepared should she meet the Royals.
''This is a once-in-a-lifetime opportunity and I'm stoked to be there. I just hope, if I do get to meet the duchess, I don't clam up and say nothing,'' Annabelle said.
Fellow classmate Sam Clark said his mum was ''really happy'' when he told her the news and that he ''might shake the duke's hand'' if he got the chance.
''It's certainly most children's dream to meet a prince and princess and they're really happy to be involved,'' Mrs Winders said.
''They can't stop talking about it.''