Gerald Pearce, father of St George's player Ana, said the girls were "devastated, confused and stunned" they were not in the final.
"Apparently the scorecard from the semifinal the week before was not handed in after the match against Rutherford," Pearce said.
"Rutherford had scored the game, but when our coach went to pick up the scorecard, they had gone and the card wasn't handed in.
"Netball Whanganui called it a clerical error, but then refused to change the draw."
Pearce said while it may have been a clerical error, it was not St George's fault — "and, anyway, everyone knew we had beaten Rutherford in the semifinal".
Rutherford were named in the final to play Tupoho School, but they couldn't put out a team and defaulted.
"Rutherford told us the week before that even if they had won the semifinal they would be unable to play in the final because they would not have the numbers," Pearce said.
"There were a lot of disgruntled parents out there and our players were hugely disappointed.
"They had worked their butts off the whole season and, despite being unbeaten, didn't get to play in the final."
He said Netball Whanganui should be "ashamed".
"This sort of thing should not happen at any level, but these girls are all just entering their teens and especially vulnerable.
"They want to keep kids in the game, yet pull a stunt like this — it's shameful."
Netball Whanganui chairwoman Nicole Dryden declined to comment other than to say the organisation was working with St George's to resolve the situation.
"It's too late now," said Pearce. "But all credit to the girls who went out to make the best out a bad situation and win their play-off for third on Saturday.
"That was a gutsy effort."
