Most schools require girls to tie up long hair into a ponytail, and boys may not have a fringe that touches their eyebrows. Dyeing and hair gel are forbidden in most schools, too.
These hairstyle guidelines are all-too-familiar to most Hong Kong students.
"School is a place where students develop a disciplined mindset. Whether they like it or not, having a clean and tidy haircut is part of the school rules, and every student should learn to obey and respect that," says Ng Kay-kong, dean of students at Diocesan Boys' School.
It is natural for schools to have their own rules of conduct, so guidelines on hairstyles are there for a reason. But many students complain that they have not moved ahead with the times. They say that rules on physical appearance make unreasonable demands on students, and that they run against the whole idea of creativity and innovation.
Like many Hong Kong schools, Mimi Lam Cheuk-ying's school, St Margaret's Co-educational English Secondary School, limits girls to two colours of hairbands - black and blue - but she doesn't see why girls may not use other colours.
Ng Ka-wing, a student at Pentecostal Lam Hon Kwong School, agrees that a hairstyle is a means of expression that should not be controlled.
"Teenagers care a lot about their appearance, and the kind of hairstyle preferred by schools makes students look ugly," says Ka-wing. "Teachers also tend to pick on those students who like to have different hairstyles. For example, during our annual athletics meet, students whose hairstyles failed to comply with school rules were asked to sit at an isolated stand. That was really humiliating."
Some schools take a more laid-back approach to hairstyles. Kerrie Chiu Ching-wai, who attends Singapore International School, said her school had no written rules for hairstyles, but teachers generally looked for tidy haircuts.
If hairstyles were considered to be unacceptable, teachers would issue students with a reminder.
One generalisation that can be made is that there appear to be contrasting rules on hairstyles between international and other schools.
"It really depends on the school's history," says Cheng Kwun-kit, Ying Wa College's principal.
"School rules are usually established when the school opens, and you don't see drastic changes once they are there.
Local and international schools cater to students of different backgrounds, so it is understandable that they have different school rules."
Although interpretations vary about what constitutes a tidy, clean hairstyle, there is no doubt that students would like more freedom.
Some students openly express their appreciation for the schools that take a more understanding approach.
"My school is among the freest schools in the district, says Kate Ng Yu-yan, who is a student at Queen Elizabeth School.
"The discipline department speaks only to those who have quirky hairstyles.
"Generally our school is very tolerant. I agree with its policy."