Mr Wong said a number of queries about same-sex ball partners were received each year, and resulted in a "handful" of complaints.
If the issue could not be resolved by the school, a mediator could be sent to work with principals and families, he said.
In 2011, Wellington student Malcolm Pimental alleged he was told he had to take a female date to the St Patrick's College ball, instead of his preferred option, a former St Patrick's student.
The case attracted widespread media attention and nearly 13,000 supporters on a Facebook page petitioning the school to change its stance.
At Mr Parsons' school, Queen Charlotte College in Picton, partnerless students were not allowed to attend, but same-sex couples were - under the condition they danced together.
"You cannot dance if you don't have a partner - we waltz, foxtrot, maxima, gay gordon and so on - so the difficulty is that they poach somebody else's partner, irrespective of sex, they poach someone else's partner and that leads to aggravation and that's what we try to avoid."
Marriage Equality spokesman Conrad Reyners said it was important young people were able to choose same-sex dates.
The letter says ...
"If the commission receives a complaint that a person has been excluded from attending the ball because they wanted to attend with a partner of the same sex and were denied by the school, this does raise questions of possible unlawful discrimination ..."
From Secondary Principals' Association president Tom Parsons
