He said Rotorua were alleged to have broken player eligibility rules in a match against New Plymouth Boys' High School on August 29 - a match which saw Rotorua qualify for the National Top 4 - but they were cleared of any wrongdoing following an investigation.
He made it clear there were no other allegations brought against them which could affect their status as New Zealand 1st XV champions this year.
However, issues were raised at the weekend, which have been widely reported, relating to the Super 8 competition contested earlier in the year.
The Super 8 includes eight boys' high schools from Hamilton to Palmerston North and is completely separate from the National Top 4.
It also has no bearing on qualification for the National Top 4.
The Rotorua Boys' 1st XV finished second in the Super 8 this year and have been relegated to last place in that competition.
Super 8 chairman Tauranga Boys' College principal Robert Mangan said evidence was produced that showed Rotorua Boys' had fielded more new players than the allowed-for six players in the final of the Super 8 competition against Hamilton Boys' High School.
Rotorua lost that match anyway, finishing runners-up.
Grinter said the breach was an honest mistake regarding two of their returning players.
He said the New Zealand Secondary Schools Sports Council had made changes to rules about what constitutes a new player at a school.
He said the changes were put on the NZSSSC website at the end of April, but the school were not aware of them until it was too late.
He said the two students in question had spent all their high school years at Boys' High and left on a gap year.
They returned to Rotorua following a bereavement and re-joined the school this year.
Grinter said they followed the rules in declaring the boys for their first match back against Hamilton, but did not realise under the new rules they would be regarded as new players.
Grinter said it was a "technicality" and once they found out about the new rule they abided by the new criteria.
The Super 8 has been running since 1997 and started with the eight central North Island schools contesting cricket and rugby.
It now includes many other sports and activities.