Many schools have these pages, on which current students and alumni are encouraged to submit messages anonymously. The pages are regulated by a group of mysterious administrators, who only upload posts after they are reviewed.
"We want all students and alumni to know more about the school and have fun," says the founder of MCS (Maryknoll Convent School) Secrets, who's an alumna of the school and now in her second year of university.
She says she sees about 200 secrets daily.
While disciplined users share sentimental stories and fun facts about their schools, some groups have been criticised for allowing embarrassing tales of students and teachers to be posted.
So, the MCS Secrets' administrative team have a rule: "We won't publish anything which accuses a teacher of being bad or pretentious," the founder said. "But if it's said in a joking manner, like one which called a teacher Hamburglar, it's OK because that teacher admits that, too."
Fukien Secondary School vice-principal Lita Chau says the pages are good platforms for students to share their views, but leaving their names should be required so that they learn to take responsibility for their comments.