"Secrets" sites have spread to the city's secondary schools, raising concern among educators and pupils about the effect of usually private chatter becoming public knowledge.
"The whole school has been talking about it since it went viral," said Mondi Ho, a Year 13 student at South Island School, where SIS Secrets garnered more than 500 likes before being shut down yesterday.
"Some of the secrets were funny but many are just plain mean."
The "secrets" range from typical high school in-jokes and teasing to complaints about teachers and banter usually confined to classrooms and school buses.
Other posts take aim at teachers. "I remember the first time [the teacher] called me 'babe'… I was so scared," one post read.
Graham Silverthorne, principal of the English Schools Foundation school, said the site seemed like "generally harmless internet chatter" but was abused by a small number of students.
"This is valuable education for our students about the danger of leaving an electronic trail on the internet in terms of future jobs and career prospects," Silverthorne said.
So far the phenomenon has been found at only one of the foundation's 15 schools, but an alternative site exists for students of Hong Kong's "elite" secondary schools, which includes ESF schools and others such as Li Po Chun United World College and Diocesan Girls' School.
"Secrets" sites began showing up early this year, but the most popular sites, all based around Hong Kong's best known universities, gained a rapid following in the last month, with thousands liking the pages on Facebook.
An ESF spokeswoman, Susanna Chiu, said yesterday that Facebook had closed the site, as it was "in violation of copyright".
"It is important for everyone to realise that some of the posts on the page are disrespectful," the school's head girl, Janis Wong, posted on her Facebook account. "There is a fine line between humour and defamation."
[Note: The article has been amended to take out references that ESF teachers had spoken to students and asked them to shut the site down, according to an ESF spokeswoman. ]