However, Year 11 students of Mount Maunganui College who spoke to the Bay of Plenty Times yesterday said the app's popularity was fading fast.
It usually held user interest for about four days before "it got boring," one said.
Jack Johnson, who had used the app, said the hype around it had already died down.
"I was only on it just to see if my name came up," said Jack.
"It was good but then it just got old."
Although the school had blocked the app on its network, students could still access it through their personal internet connections on their smartphones, he said.
Fellow student Heidi Phillips said the hype was around "people talking about other people".
"People stopped talking and it just got boring," she said.
Joseph Wallace and James Cornelius said some students had used it to bully while posting anonymously.
"It's just nasty stuff ... and people don't know who it's from." said James.
"It was just things like girls who wear too much make-up," Joseph said.
Another student said the app was not as popular with Year 12 or Year 13 students.
Netsafe was aware of Yik Yak.
Young people had been using the app to "abuse and harass" because they can get away with it anonymously, said the organisation's training and education specialist, Lee Chisholm.
Most bullying reports were from parents or teachers of intermediate and high school students.
