Wellington College is investigating social media posts made by two students describing sex with drunk women in a closed Facebook group.

Some of the comments had been 'liked' by other students, RNZ reported.

"If you don't take advantage of a drunk girl, you're not a true WC [Wellington College] boy," read one of the comments, believed to have been posted on Sunday night.

The parents of concerned students had been told about the posts by their sons, as had Wellington College Principal Robert Moses, who was notified by a member of the public.

Moses told RNZ the school was now investigating, saying he was "appalled and disgusted" by the comments.

He added that the boys who made them were "shattered" by what they had done.

"I think the boys are absolutely distraught about what has happened. I don't, in any way, want to minimise what was said, but at times there is bravado that can happen on these websites, and I think that is probably what has happened."

Moses said the posts showed the problem schools had with immature students being able to post what they wanted in closed groups.

"We can say the right messages in assemblies, we can have the right programmes in place, we can push the right values, but at times, regrettably, in the privacy of these chat rooms that we don't have access to, idiotic boys can say things that are very, very sad, and that's what's happened on this occasion."

Wellington College was currently trying to figure out if the comments had been posted during school hours.