"She has been absolutely ripped off and I think it is totally unfair," Mr El-Agez said.
"When she came here, she was in primary school and they put her at an appropriate learning level, which is totally beyond her control.
"Her birthday is in July so yes she is a bit older than the others ... but it certainly doesn't give her an advantage.
"She plays in the back and she's the shortest in the team so that's certainly not an advantage."
Mr El-Agez said Chelsea hadn't played volleyball longer than any of her teammates.
Chelsea tried to keep her emotions in check at training yesterday but it wasn't long before tears were streaming. "It's unfair, not just because I'm in this position but I think it would be unfair for anyone," she said.
"No one realised there was an age restriction and because I am in Year 10 it hasn't been picked up until [a month ago].
"I'm so upset."
Chelsea said she "didn't have a choice" what school level she was put into when she came to New Zealand and felt "absolutely gutted" she could not play in next week's tournament.
Before he went to VNZ, Mr El-Agez approached all of the Western Bay volleyball coaches - who would directly be affected in the upcoming tournament - and argued his case that Chelsea should play. All six coaches agreed.
In early November, Mr El-Agez applied for special dispensation from VNZ to allow Chelsea to play. Operations manager Julie Carpinter sent his application to the North Island, South Island and secondary schools advisory groups and collectively the decision was made to reject his request.
"There has been some robust discussion amongst the group but by majority your request has been declined," Ms Carpinter wrote.
"This decision is consistent with other requests that have been considered this year."
A representative from VNZ said the rule was specific to the junior competition and had been around for "a significant number of years". "The rule is clear - the players must be in Years 9 and 10 at college and under the age of 15, as of the first of January. This rule is stated clearly in the manual."
Four people had applied for dispensation this year in relation to the age rule - and all were denied.
The representative said there would be an opportunity to look at the eligibility rule at an advisory meeting after the tournament.
Mr El-Agez has instead made Chelsea his assistant coach.
"If I'd have known she was not eligible to play [in the tournament] then I wouldn't have picked her last year.
"It's as simple as that. This system has let her down, it's let me down and it's let the rest of the team down ."
The Mount Maunganui College team are seeded first for the event after winning the Bay champs..