In banning the app, Takapuna Grammar principal Simon Lamb said while it recognised the often positive contribution technology grants to education, it had concerns about the misuse of Yik Yak.
"This action alone sends a strong signal to our parents and students, raising our community's awareness of the issue and its potential misuse."
Diocesan also blocked access for its students after students reported problems with bullying and nasty comments after the app went viral at the school within a lunchtime, as hundreds of students downloaded it to their smartphones.
Parents were also warned of its dangers through newsletters and information programmes.
"We're delighted our girls identified Yik Yak as an issue," said principal Heather McRae. "We teach them the values you have as a person should be the values you have online."
Yik Yak works on a geographic basis, like a giant message board.
It allows students to post comments anonymously, and only those within a 16km radius can see what's happening. They can then "up vote" or "down vote" comments.
If a comment, or "yak", gets many upvotes, it gets a high score, rewarding the user with "yakarma". Messages can also be commented on, starting a thread of conversation.
"It's the ideal situation for a bully," said Netsafe head Martin Cocker. "The identity of the bully is most likely known to the victim but not easily identified by authorities, so abuse is very difficult to prove."
Mr Cocker said Netsafe had received calls from some schools about the app. It had been "on the radar" after schools and universities in the United States reported similar problems with the app.
Mr Cocker said while banning Yik Yak was an option that could disrupt its use, the best thing to do was to talk to students about online behaviour and encourage positive use.
Overseas, Yik Yak has responded to criticism about bullying and harassment by geoblocking high schools, preventing students on site using the app.
TechCrunch reported the app had now "fenced" 100,000 schools in the US and it was "still one of the first steps the company takes as it moves into new countries". It had not blocked high school areas in New Zealand, however.
Yik Yak did not respond to a request for comment yesterday.
Several media outlets have called for the app to be banned; the Huffington Post said it was "useless" and the New York Times called it a "virtual bathroom wall".
High schools are warning students off an anonymous messaging app described as a "virtual bathroom wall", with some Auckland principals so concerned they've banned it outright.
What is Yik Yak?
• An anonymous social media app that allows people to make posts and comment on others' posts within a 16km radius.
• Posts can be "up voted" or "down voted" giving users a success rating.
• It was released in 2013 and has received negative feedback in the United States, where it was criticised for contributing to bullying and harassment in schools.